# Comptometer

The Comptometer is a mechanical calculation machine. It was invented Dorr E. Felt, and made by the Felt & Tarrant company in Chicago, USA. Felt gave a lecture about the history of mechanical calculators, which was published in 1916, and in it he briefly mentions how he came to make the first prototype of the machine in 1885. Its various models were in production from 1888 to 1961, peaking during the 1930s.

The "shoebox" case of the most common models is made of copper plated steel that is painted brown. Any Comptometers that seem to be made of shiny copper have had their original paint stripped or polished away.

The keyboard usually consists of 8, 10 or 12 columns. Each column has 9 buttons numbered 1 to 9 from nearest to furthest. To help with touch-typing, the tops of the even-numbered keys are almost flat, while the odd-numbered keys are concave.

In front of the keyboard there is a register. It is a row of small round windows through which you can see the digits of the calculation result. There is one more window/digit than there are columns of keys.

A top plate of the case extends some distance beyond the keyboard, and onto this is attached a chromed plate that bears the "Felt & Tarrant" name.

## Calculation

The Comptometer is a direct adding machine. This means that when you press and release any of the numbered keys, its value is immediately added to the total shown in the register. Adding a set of numbers is therefore as simple as typing them all in. It has "duplex" functionality, meaning that it is possible to press keys from different columns at the same time to speed thing up.

The large lever on the right will clear the register, setting it to zero.

Subtraction is done by adding the tens-complement. The small digits on the keys are helpful for achieving this. To subtract a number, you must first mentally subtract 1, and then type it using the small digits. Precede the number by as many leading zeros (actually nines) as is needed to reach past the left of the current value in the register. The small metal tabs are used to block a carry, and using one here avoids the necessity of pressing any further leading zeroes in the number you are subtracting.

Multiplication is done by repeated addition. If you can press the keys for entering one of your factors all at the same time, it is easy to press that set of keys several times to get multiples of that number. Shift your fingers one column to the left to add multiples of ten times your number, and so on for higher columns.
For example to multiply 6798 by 24, press 6798 down four times in the last 4 columns, shift a column to the left and press the same pattern of keys twice.

Many tricks were devised for other kinds of calculations. To increase speed and touch-typing accuracy, operators often only used the bottom half of the keyboard. Instead of entering a high digit such as 8 directly, they would press 4 twice. This reduces the need for hand movement, and is easier to do without looking.

## "Controlled-Key" mechanism

If you press down on a key but release it before it is pressed all the way in, the mechanism of the Comptometer would not be able to register the digit you wanted. To avoid this leading to calculation mistakes, a safety mechanism was used. When a partial key press occurs, all the keys in the other columns become locked. The partial key press will not have affected the number in the register, so you can then press the intended key completely to rectify the problem. You will have to press the red button at the back right to release the locked columns to continue.

## Videos

Here is a video where I demonstrate the various features of my Model J Super Totalizer Comptometer.

In this video I demonstrate how to do the four basic arithmetic operations on the Comptometer.

This video shows the Model E Comptometer.

## Comptometer Simulator

I have created a simulation of the Comptometer using javascript. If you click the link below, the simulation will open in a new window. If you are using a touch screen, then on most browsers you will be able to press multiple keys at the same time.

## Models

The first model (with a wooden case) and the subsequent models A to E are very rare, and won't be discussed here in detail. The most common shoebox models are F, H and J. The serial number limits are based on observed examples, so machines with numbers outside these ranges may exist.

Wood 1887-1903 10-6244 6300 Wooden case
Front of case is right-angled, with a flat glass window over the register.
Complicated clearing mechanism with a wheel and a small lever.
A 1904-1906 15000-20603 5700 First model with copper-plated steel case.
Front of case is right-angled, with a flat glass window over the register.
First model to have Duplex (multiple key press) functionality.
First model to have a clearing handle.
B 1906-1909 25000-33461 8500 First with S-curve shaped front of case.
Carry-blocking tabs are shaped and closer to keys.
C 1909-1912 35000-38602 3700 Keys made of composite
C-light 1911-1912 40000-48648 8700 Keys made of celluloid
Lighter key action
D 1913-1913 49000-49154 200
E 1913-1915 54000-61612 7700 First to have the Controlled Key system.
Only model to use guards on the side of the keys to detect inaccurate keystrokes.
White Controlled Key release button
F 1915-1920 100000-142337 42400 Front side panel of case has no decoration.
Clearing lever pivot is located just beyond the 9 keys.
Clearing lever angled towards the user.
Rear side panel of case lists series of patents.
Embossed decoration on the side panels is the same colour as rest of the case.
First with a red controlled key release button
Keys are black and white.
H 1920-1927 200000-248508 48600 Front side panel of case has Comptometer logo.
Clearing lever pivot is located between the 4 and 5 keys.
Clearing lever angled vertically.
Rear side panel of case has Comptometer logo. The name plate lists the patents.
Decoration on the side panels of the case are painted black to contrast with the case.
Keys are black and white.
Case is a centimetre longer at the front, with the S curve less steep, to make room for the new clearing mechanism.
J 1928-1938 J245489-J346384 100900 The serial number is preceded by the letter J.
Keys are green and white.
K 1934-1950 350000-?????? Electrically driven.
Metal casing, painted very dark brown.
Keys are all the same length.
Casing has a rear leg to tilt the keyboard.
Clearing lever ends shaped like a tab rather than a round handle.
M 1939-1950 400000-?????? Rounded metal casing, painted dark green.
Clearing lever inside the casing instead of on the side.
New Comptometer logo on the front.
Carry-blocking tabs have small white/green key tops.
First with shutters that hide leading zeroes automatically.
3D11 1950-1957? Controlled-key release button in front of keyboard, and green instead of red.
Automatic Controlled-key release button on the left of keyboard, useful in multiplication/division.
No Comptometer logo on the front.
Decimal pointers are below the register.
992/99C 1950-1961? Electrically driven version of the model 3D11.
No automatic Controlled-key release button on the left of keyboard.
No Comptometer logo on the front.
Decimal pointers are below the register.
616CE 1957-1961? Better known as the "Customatic".
Electrically driven, similar to the 992.
Electric clearing mechanism.
A slider to the left of the keyboard for setting the "Customatic Key Control".
Light grey casing.
Decimal pointers are below the register.

There is little or no external difference between the H and J models. They use exactly the same casing, and even their serial numbers overlap during the time when the stock of H model mechanisms were used up and the production of the J model mechanisms was built up. There were apparently several internal mechanical improvements, so the ones with the improved mechanisms had their serial number preceded by the letter J. They started using green keys on the model J instead of black ones, but as keys were often replaced this is not a completely reliable characteristic.

The electrically driven model K was like an electric typewriter in that the electricity was used to generate the force needed to activate the mechanism so that the key presses could be kept very light. It had a redesigned case that raised the rear end so that the keyboard sloped at the same angle as the previous models to compensate for the fact that all keys now had the same amount of travel.

The model M also has a variant built during the war, dubbed the model WM. Due to a metal shortage its parts were redesigned to use less metal (e.g. internal plates and levers were thinner and had holes punched in them). It looks the same as the normal model M but is much lighter in weight.

## My Model E Comptometer

This is a 12-column Model E Comptometer. This model was the first to include the "Controlled-Key" error detection, but also has guards on the side of the keys. If the metal guard is pressed down without first pressing the button itself, then the key will not travel further. This guards against the user accidentally catching an adjacent button during a button press. This system was dropped in subsequent models, probably because it was too complicated, the keys were prone to breaking, and because the problem it is guarding against is not common in trained operators.

My machine has serial number 56337, and was made in 1913 or 1914. This Comptometer is in fairly good condition, except that the left-most column of keys is locked. Presumably the guard system for that column is stuck. The zeroing mechanism often fails to fully reset when the handle is moved slowly. The Controlled-Key reset button is normally white in the Model E, but has been replaced here with a later red one. Some of the keys have broken during its working lifetime causing the key rod to come away from the flat stem of the guard. These keys have been patched up either by binding them together with a bit of metal wire, or by riveting them together with the key in the depressed state, effectively disabling the guard for that key. It is interesting to see that the base plate of the case for the 12-column model was built by joining together two smaller ones.

See the Video section on this page if you want to see the key guard system in action.

## My Model J Comptometer

This 10-column Model J Comptometer looks rather different from its original state. In the late 1940s or the 1950s it has been reconditioned, during which the casing has been wrinkle painted green, and the key-tops replaced with those from a model M or later. It has unfortunately been stored in poor conditions - the paint has discoloured and has begun to flake off.

Its internal mechanism is in fine condition, and needed only a little bit of lubrication to make it work perfectly.

This machine has serial number J314420. It has been said that the first two digits of the J number roughly match the year of production, but that is not quite accurate. The numbers range from about J245489 to J346384, which were produced from 1926 to 1938, so the machines were made about 2 to 4 years later than the first serial number digits indicate. My machine was therefore probably made in 1934.

## Super Totalizer

A special version of the Model J was made, called the Super Totalizer. The mechanism and case of the model J is extended at the front to add a second register. This register has a lever on the right that causes the number shown on the normal register to be added to it, and which also then clears the normal register. The lever on the left clears the extra register.

The extra register also has a row of buttons that when pressed and locked down move a cover over the corresponding digit to hide it. Any carry operation from a covered digit to a still visible one is suppressed.

This version has the normal J serial number, but also a second serial number especially for the Super Totalizer. I found the following numbers in other online collections:

J numberS numberKeyboardSource
J315804S73910 columnsPaul Breedveld
J316912S84310 columnsFred Haeghens
J316821S11318 columnsRechenmaschinen illustrated, H.van Noort
J317799S130812 columnsJay M. Goldman
J317808S131812 columnsComputarium, François Koeller
J317834S133512 columnsWorthpoint / eBay
J317903S141512 columnsMy own.
J321777S162510 columns, sterling (no farthings)John Wolff
J324639S185410 columnsComputer History Museum
J324720S192810 columnsRechner lexikon, Valéry Monnier
J324725S195710 columnsCris vande Velde
J327695S232112 columns, sterling (no farthings)John Wolff, not shown on his website
J339128S25948 columnsCris vande Velde
J339163S26208 columnsNational Museum of American History
J342586S270812 columnsOnline auction
J345247S315010 columnsMy own. In very poor condition.

It is not clear whether the S numbering started at 0 or 500, and it probably did not go further than 3300, so it is likely that between 2800 and 3300 Super Totalizers were produced.
Between S1308 and S1415, the S numbers rise a little faster than the J numbers. This might mean that some previously produced J Comptometers were being converted to STs. Note also that the second and third ones on the list have contradictary numbers.

For some reason the Super Totalizer was hardly ever shown in advertisements. Instead, the electric model K was promoted much more heavily. There was no Super Totalizer version of the model K, but later there were ST versions of the mechanical model M. It seems that the ST models were more popular in Europe and India than in the USA.

## My Super Totalizers

Here are some pictures of my Super Totalizer (J317903/S1415). It is in very good working condition, but has had some repairs or restoration done. In particular, 9 of the key tops have been replaced with reproductions, and the celluloid windows have been replaced with more modern plastic.

I have recently acquired a second ST in rather poor condition (J345247/S3150), but which can be used for spare parts. It has 10 columns of keys, but their plastic tops have degraded, and some of them are missing. The black and white ink of the key numbers had expanded and spread, so I have cleaned the keys before taking these pictures. The clearing handle is badly bent, some screws are missing, as is one of the extra register's blinds and its plastic window. The mechanism had seized up, especially the mechanism of the extra register, but I have managed to get it mostly working again just by spraying in some silicone lubrication. Unfortunately the clearing mechanism tends to get stuck and I have not yet found the cause of that.
The most interesting thing about this ST is its late model number, which allows a fairly accurate estimation for the number of model ST Comptometers produced.

## Books and Manuals

Methods of Operating the Comptometer    (PDF, 13.3 MB)
Felt & Tarrant Mfg. Co., Chicago, U.S.A.
36 page stapled booklet
128mm × 180mm

This booklet is the original standard manual for using the Comptometer. It starts with directions for oiling, and then explains addition, multiplication, subtraction, and division, as well as some more advanced techniques such as common fractions, Stone measure, British currency, compound interest, discounts, and square roots.

The version shown here is a first edition from 1895, when the Comptometer still had a wooden case and only one key could be pressed at a time. There are revised editions of this manual until 1928, after which it was superseded by "Easy Instructions for operating the Controlled-Key Comptometer".

My copy has a library stamp on the front cover that says "Library U.S. Patent Office, Nov 29 1896", and inside is written in pen "Writen by D.E. Felt.". The page that describes oiling of the mechanism has been stamped with the text "Oiler given when Comptometer is billed". This may refer to the small oil can shown in the Paraphernalia section.

Methods of Operating the Comptometer    (PDF, 19.1 MB)
Felt & Tarrant Mfg. Co., Chicago, U.S.A.
58 page stapled booklet
126mm × 178mm

This is the 1911 edition of the above standard manual for using the Comptometer. It has now expanded to 58 pages, though it tackles exactly the same set of subjects.

This version is from just before the "Controlled-Key" mechanism was introduced, so the illustrations and photos use the model B or C Comptometer. The later editions of this manual from 1920 and 1928 do describe error correction. This manual was later superseded by "Easy Instructions for operating the Controlled-Key Comptometer".

Note the presence of the shield logo - a shield with the symbols of the four arithmetic operations on it, with Comptometer written across the top. This logo would often be used in printed material, as well as the rings and badges, but never on the Comptometer machines themselves, and rarely in advertising.

Methods of Operating the Comptometer    (PDF, 20.3 MB)
Felt & Tarrant Mfg. Co., Chicago, U.S.A.
1928 (Copyright 1895, 1904, 1911, 1913, 1915, 1916, 1920, 1921, 1928)
68 page stapled booklet
136mm × 196mm × 4mm

This is the 1928 edition of the above standard manual for using the Comptometer. It has now expanded to 68 pages, mostly by having additional pages inserted at the start before the main text. These pages deal with oiling, the Controlled-Key mechanism and error correction, and the features of the clearing mechanism of the model J.

This seems to be the last edition of this book. This manual was superseded by the simpler manual "Easy Instructions for operating the Controlled-Key Comptometer".

Handleiding voor de behandeling van den Comptometer    (PDF, 9.71 MB)
Felt & Tarrant Mfg. Co., Amsterdam
1919-1920
26 page stapled booklet
142mm × 204mm

This booklet is a Dutch manual for the Comptometer. It is a shortened version of the Methods of Operating the Comptometer booklet above, leaving out the directions for oiling and the more advanced calculation techniques. It explains the "Controlled-Key" mechanism, addition, multiplication, subtraction, and division.

The illustrations in the booklet show the model F Comptometer. There is no publication year inside, but it probably dates from 1919 or 1920 because it says that the Dutch office of Felt & Tarrant was in Amsterdam, Koningsplein 1. I found confirmation elsewhere that their address in 1915 was Damrak 28-30; from there they moved to Koningsplein 1 in May 1919 where they stayed till at least 1926; according to the corrections in this booklet they moved to Rokin 84 at some later date; and finally in about 1934 they were located at Hendrikkade 20-21. They kept the same telephone number throughout, apart from the addition of a digit when the telephone exchange was upgraded.

Comptometer - Méthode Pour Opérer    (PDF, 18.9 MB)
Felt & Tarrant Mfg. Co., Paris
1915-1920?
48 page stapled booklet
135mm × 210mm

This booklet is a French manual for the Comptometer. It is a translation of the Methods of Operating the Comptometer booklet above, even including the sections on British currency and Imperial weights.

There is no publication year inside, but it probably dates from 1915-1920, as the illustrations show the model F Comptometer. It included a card with a further explanation of how to use the Controlled-Key mechanism and correcting errors.

Easy Instructions for operating the Comptometer     (PDF, 11.7 MB)
1915
Form 112 (booklet), Form 96 (card)
12 page stapled booklet
217mm × 281mm (booklet), 104mm × 167mm (card)

This booklet is a simplified manual for using the Comptometer, containing only the basic methods that can be found in the "Methods of Operating the Comptometer" above. It explains addition, multiplication, subtraction, and division.

It has no copyright year, and strangely does not mention the company Felt and Tarrant anywhere. The version shown here is from approximately 1915. Its title is listed in The 1911 Register Of Copyright Entries, and while the text is probably from that year, the pictures on the front and inside have been updated to show a model E, and a picture on the back shows a model F. A small card was included to explain the Controlled-Key mechanism and error correction. A French version of that card can be seen above that was included with "Méthode Pour Opérer"

This booklet was expanded in later versions, and eventually became the main manual for the Comptometer, taking the place of "Methods of Operating the Comptometer". Various later versions of this booklet can be found below.

Easy Instructions for operating the Controlled-Key Comptometer Adding and Calculating Machine    (PDF, 14.3 MB)
Felt & Tarrant Mfg. Co., Chicago, Ill.
1920
Form 112
22 page stapled booklet
184mm × 235mm

This is the 1920 version of the above booklet, which is a simplified manual for using the Comptometer. It still explains addition, multiplication, subtraction, and division, but now has been expanded to explain the "Controlled-Key" mechanism. At the end it has a list of the various tables that were available, some of which you can find in the Tables section of this page.

Easy Instructions for operating the Controlled-Key Comptometer    (PDF, 12.5 MB)
Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
1941 (?)
Form 1017-L
22 page stapled booklet
167mm × 205mm

This booklet is the basic manual for using the Comptometer. By this time it had fully replaced the more complicated "Methods of Operating the Comptometer". It has 19 pages plus 3 pages of tables. It explains addition, the "Controlled-Key" mechanism, multiplication, subtraction, and division.

The version shown here is from the 1940s, possibly 1941, but there is no publication year inside.

Easy Instructions for operating the Accuracy Key Comptometer    (PDF, 10.7 MB)
Comptometer Corporation, Chicago, Illinois
1958
Form 1017-R
22 page stapled booklet
164mm × 203mm

This is the 1958 edition of the basic manual for using the Comptometer. It is virtually identical to the 1940s edition, except that all photographs and drawings were updated to new models, and the page about the Controlled-Key (now the Accuracy Key) has been rewritten.

One interesting change is the claim in the introduction that there are now eight different standard sizes of comptometer. Whereas there used to be only 8, 10, 12 column keyboards as standard, with a 20 column version for special statistical work, there are now apparently also 5, 7, 9, and 11 column versions. The Customatic shown in the photo on that page does have 9 columns.

Instruction Manual for the Operation of the Comptometer    (PDF, 17.1 MB)
Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
1944
32 page ring bound book
217mm × 280mm

This instruction book was used at Felt & Tarrant Comptometer schools. It consists of 32 leaves of thick paper printed on only one side, and bound at the top edge by two metal rings. It covers the basics of arithmetic in 14 lessons, and it would take about 13 days to teach. According to its table of contents, there were about three more similar course books to follow for the full 3-month course. It may be that the original owner of this manual followed only the short introductory course.

My copy of this book has the name Gene Fleming written on the front, and some of the answers have been filled in.

Courtesy Course of Instruction For Use Only With The Comptometer Adding-Calculating Machine    (PDF, 20.2 MB)
Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
1947
Form 1204-F
40 page stapled book
183mm × 230mm

When a company bought one or more Comptometers, as a courtesy Felt & Tarrant would offer to train some of the company's staff in the use of the Comptometer. This course book was used for such a training course. It covers the basic methods of performing arithmetic in great detail, and includes practise exercises along the way.

Applied Mechanical Arithmetic as practised on the Controlled Key Comptometer Adding and Calculating Machine.
Felt & Tarrant Mfg. Co., Chicago, Illinois
First Revised Edition
606 page bound book
183mm × 148mm × 32mm

This book goes into great detail how the Comptometer can be used in various business processes. Mine has the name "Miss Ideus" written on the first page. The book contains prints of several photographs showing the Comptometer being used in the workplace. Pictures of most of those pages can be seen below.

A complete scan of the 1914 edition is available from the Internet Archive, available as a pdf file and in many other formats.

Table of Reciprocals For numbers from 1 to 10,000    (PDF, 33.8 MB)
To Be Used in Connection with the COMPTOMETER
Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
Form 192
50 page stapled booklet
178mm × 253mm × 5mm

This booklet contains a table with the decimal expansions of 1/n for n up to 10,000. There are 10 pages of introduction, followed by the table on 40 pages which are tabbed for quick access. It has a sturdy cardboard cover, slightly larger than the pages.

Although the text has a copyright of 1917, the version shown here was printed in the 1940s because the title page has a picture of the model M, and the cover mentions the Comptometer Division of Felt and Tarrant. The 1917 version has the longer subtitle "to Be Used in Connection with the Controlled Key Comptometer Adding and Calculating Machine".

There are three minor mistakes in the table. The reciprocals for 118, 185, and 476 were erroneously rounded up instead of down in the last decimal. These errors may have been deliberately introduced as copyright traps to recognise illegal reproductions.

The Comptometer Course in Business Arithmetic.    (PDF, 88.0 MB)
Compiled for use only in the instruction of the operation of the Comptometer - adding and calculating machine.
Felt & Tarrant Mfg. Co., Chicago, Illinois
Revised Edition
Form 1004-E
195 page bound book
193mm × 254mm × 14mm

This book opens vertically, like a notebook. It has 195 pages - pages 1 to 96 on one side, and then turn it over to get pages 97 to 195. It contains a great many exercises, with which to practice working on the Comptometer.
There is also a 1935 version of this book, titled "Business Arithmetic for use only with the Comptometer", later editions printed in 1947, 1951 and 1954 with the title "Comptometer Course for Business Training", and a final edition from 1958 titled "Comptometer Course For Business".
In my copy of the book, many of the pages have answers penciled in. The front flyleaf is inscribed "Maxine Fick, 5069 N Damen Ave., Chicago, Ill." with the telephone number "Ravenswood 2264". At the time of the 1930 US census she was 13 years old. Underneath is written "Bryant & Stratton College, 18 S. Michigan", which is a chain of business schools. I found an online image of an advert for this school from 1937.

Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
Form 1004-S
304 page bound book
185mm × 255mm × 22mm

This is the 1954 edition of the book that was previously called "The Comptometer Course in Business Arithmetic" (1925, 1931) and "Business Arithmetic for use only with the Comptometer" (1935).
The book opens vertically, like a notebook. It has 304 pages - Part One consisting of pages 1 to 152 is on one side, and if you turn it over you have Part Two, also with pages numbered 1 to 152. It contains a great many exercises, with which to practice working on the Comptometer. It covers the same subjects as the previous editions, but in a less terse manner.
My copy of the book is in good condition, and only a few of the pages have answers lightly penciled in.

Adding Practice Book To Be Used in Connection With the COMPTOMETER
Felt & Tarrant Mfg. Co., Chicago, Ill.
1920-1925?
Form 319
80 page spiral-bound book
89mm × 233mm × 10mm

This small spiral-bound exercise book has thick cardboard covers and contains 78 pages which each have a single column of numbers to be added using the Comptometer. It shows no copyright year, but the form number and the picture of a model H mean it probably dates from the early 1920s.

Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
Form E-1257
86 page comb-bound book
146mm × 217mm × 10mm

This comb-bound exercise book has thick cardboard covers and contains 1 page of text followed by 393 sums to be done on the Comptometer.

Manual of Instruction and drills to be used with Comptometer Educator    (PDF, 7.48 MB)
Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
1950?
Form 1389
36 page stapled booklet
139mm × 178mm

This booklet with exercises came with the Comptometer Educator (see the Paraphernalia section). I don't know its year of publication, but it is probably some time in the late 1940s or early 1950s.

Comptometer Course
58 page staple bound book
228mm × 288mm × 8mm

Apart from books by Felt & Tarrant themselves, there are also books by others such as this one. It is similar to the Business Arithmetic course book above, also opens vertically, but is printed on only one side. It has 54 pages covering 51 lessons, but there are also 4 loose pages inserted at the back covering lesson 117. Note that the book also mentions the Burroughs calculator, a cheaper rival calculator that is very similar to the Comptometer but without the error detection mechanisms.
The front of this course book has been signed with the student's name, Eileen Powell.

How to Use the Calculator and the Comptometer    (PDF, 50.1 MB)
By James R. Meehan
Third Edition
128 page stapled book
217mm × 280mm × 7mm

This is another course book for both the Comptometer and the Burroughs calculator. It consists of 40 lessons, with an emphasis on addition, but also covers subtraction, multiplication and division. Its pages have perforations, so that when the answers to an exercise are filled in, it can be torn out and handed in to the teacher. This may make this book somewhat rare to find despite having been very widely used as an alternative to Felt & Tarrant's Comptometer Course for Business Training. There were five editions - 1940, 1947, 1952 (shown here), 1959, and 1964.

Key-Driven Calculator Course
By Raymond Charles Goodfellow and Peter Lawrence Agnew
Second Edition
167 page book
213mm × 272mm × 9mm

This is also a course book for both the Comptometer and the Burroughs calculator, and it contains 59 jobs. As with Meehan's book above, its pages are designed to be filled in and torn out as they have perforations near the spine, and this may make it somewhat rare to find this book intact. Shown here is the second edition from 1942, but the 1949 third edition follows below.

Key-Driven Calculator Course for the Burroughs Calculator and Comptometer
By Raymond Charles Goodfellow and Peter Lawrence Agnew
Third Edition
158 page ringbound book
281mm × 210mm × 8mm

This third edition has virtually the same contents as the second edition above, but it is laid out differently because the book is now spiral bound and of a different format. Each page page has a vertical perforation at about one third of the way along. The inner third of the page contains an explanation of a job, and the detachable two-thirds has the job itself with spaces where the answers can be filled in. There was a fourth edition of this book in 1962, and also a sequel, the "Advanced Key-Driven Calculator Course" by Peter Lawrence Agnew and Mary Margaret Brady in 1958.

Kantoormachine Gids (Office Machine Manual)     (PDF, 4.69 MB)
International Office Machines Research
5 loose leaves, perforated for a ring binder.
157mm × 246mm
1939, 1940, 1951

The Kantoormachine Gids was a Dutch consumer guide to office machines. It gave detailed technical specifications of the many office machines that were available. It was printed on loose perforated pages that could be kept in a ring binder, so that as when new machines appeared on the market, new pages could be added. Presumably you could get a subscription so that you would be sent regular updates.

The 10 pages here consist of:
a 4 page installment from July 1939 describing the models J, JS (Super Totaliser), and K;
2 pages from June 1940 describing the model M;
4 pages from April 1951 describing the 992 and 3D11 models.

The Soldiers' French Phrase Book    (PDF, 13.2 MB)
Felt & Tarrant Mfg. Co., Chicago
2nd Edition
56 page stapled booklet
107mm × 134mm

This small book was published by Felt & Tarrant and given for free to American soldiers to aid them in the Great War. It contains words and phrases that are supposedly useful to a soldier in France, though for many there was unlikely to have been any opportunity to put them to use. Near the back there is an advert for the Comptometer, described as "the Machine Gun of the Office". The first page says:

In the hope that it may prove a convenient and serviceable aid to the intelligible expression in French of words and phrases necessary to communicate the common wants, wishes and desires of everyday military and social life, this French Phrase Book is presented to the soldier boys of America
with the complements of
Felt & Tarrant Mfg. Co.
Chicago

This book has a name written on the inside cover in pencil, "Wilburn C Buttler, Ft. Worth". The closest match is from the 1920 census - Wilburn C. Butler, in Fort Worth (Ward 11), Tarrant County, Texas. He was born on 8 October 1888, died on 3 April 1955, and is buried in Mount Olivet Cemetery, Fort Worth.

## Tables

Felt & Tarrant printed many small tables to help the operator with common calculations. Such tables were usually printed on thick cardboard for durability. In the 1920 edition of "Easy Instructions for operating the Controlled-Key Comptometer" a list is given of various tables that were available at that time. I reproduce that list here. The ones on this list that I own are marked by an asterisk.

Form NumberTitleDescription
1Tonnage TableGives the decimal part of a ton of any number of pounds.
3Lumber TableGives result of dividing 12 into any dimension up to 11 7/8.
4*Discount TableGives the net of chain discounts.
5Lumber TableGives number of board feet in pieces of various sizes.
6Gross TableGives the decimal for each fractional part of a gross and for each unit.
7*Grain TableGives the decimal part of a bushel of any number of pounds of different grains.
8Ten and 100 and 1000 X Inches and Fractions to Eighths TableUsed only in connection with the Engineering Model Comptometer for figuring beams, pipe, etc.
9Reciprocal TableUsed for making division quickly and easily by multiplication.
10British Currency TableGives the decimal part of a £ of any number of shillings and pence.
12British Currency TableGives the decimal part of a £ for pence and 32nd fractions.
21Quarters and Pounds of a Ton TableGives the decimal part of a ton of any number of Quarters and Pounds.
22Quarters and Pounds of a Cwt. TableGives the decimal equivalents of a Cwt. from 1/2 lb. to 3 qrs. 27 lbs.
24Interest TableGives the interest on \$1.00 for different numbers of days at different rates.
25Net Discount TableShows the net left from \$1.00 after discounting for the required number of days.
26Decimal TableUsed for figuring elapsed time. It gives the decimal part of a 360-day year up to any date.
29*Decimal Equivalents of Fractions TableGives decimal equivalents of fractions from 1/4 to 63/64.
32Cooperage TableUsed to determine how many staves of one size are equivalent to another size.
33*Interest TableGives the interest on \$1.00 for one day for rates from 1/8 % to 12 7/8 %.
35*Payroll TableGives the decimal part of a month for any number of days and eighths of days.
36Insurance Cancellation TableShows decimal part of the year for months and days.
37Figuring Elapsed Time TableShows decimal part of a year for each day.
38Pounds, Ounces, and Drams TableGives the decimals of a 16-oz. pound for any number of drams and ounces.
184Interest TableGives the interest on \$100. at 7% for from 1 to 364 days.
191Grain TableGives the Dockage and the net bushels per 1000 lbs. for different rates of dockage.
205Weights per Foot and Inch for Rounds, Squares, etc. of Different Thicknesses TableEnables one to get the weight of a piece.
234Iron and Steel TableGives the price per 100 lbs. at .01 to \$100. per gross ton.
237Interest TableUsed for figuring interest on a 365-day basis, where interest rates run from 1 to 12%.

Decimal Equivalents of Common Fractions To be used in Connection with the Comptometer.
Felt & Tarrant Mfg. Co., Chicago, U.S.A.
Series No. 2
108mm × 164mm

This card was included when I bought the 1911 edition of "Methods of Operating the Comptometer", so is likely from around that time, especially since the picture on it is of a model B or C Comptometer. The card is signed on the back by Adelina Artesani who according to the 1900 and 1910 census was born in 1894 and resident in Boston, MA.

Decimal Equivalents of Common Fractions To be used in Connection with the Comptometer.
Comptometer Division, Felt & Tarrant Mfg. Co., Chicago, Illinois
Form 29
102mm × 235mm

This card was included when I bought the "Table of Reciprocals" book, and it supplements that book by supplying some fractions that have numerators other than 1. Unlike most of the other cards, this one is printed partly in colour. It has no copyright year, but was probably printed in the 1940s as it has a picture of the model M.

Discount Table Showing net of \$1.00 after discounts, shown at top and side, are taken off.
Comptometer Co., Chicago, U.S.A.
Form No. 4
165mm × 279mm

This card has no copyright year, but was probably printed in the 1940s as it has a picture of the model M. It is likely that earlier prints of this card exist.

Grain Table Pounds Expressed in Decimal Parts of a Bushel.
Felt & Tarrant Mfg. Co., Chicago, U.S.A.
Form 7
117mm × 267mm

This card has no copyright year, but was probably printed in the early 1920s as it has a picture of the model H.

Interest Table (360-day basis) To be used in Connection with the Comptometer
Felt & Tarrant Mfg. Co., Chicago, U.S.A.
Form No. 33
225mm × 159mm

This card has no copyright year, but was probably printed in the early 1920s as it has a picture of the model H.

Pay Roll Table Decimal Equivalents of Days and Eighth Fractions of Days, for 24-31 Day Months also Minutes expressed in Decimal Equivalents of an Hour.
Comptometer Co., Chicago, U.S.A.
Form No. 35
195mm × 322mm

This card carries a copyright year of 1925, but it must have been a reprint from the 1940s as it has a picture of the model M.

Decimal Equivalents of Fractions from 3rds to 26ths inclusive To be used in Connection with the Comptometer.
Comptometer Co., Chicago, U.S.A.
Form No. 368
185mm × 235mm

This card has no copyright year, but was probably printed in the 1940s as it has a picture of the model M.

Decimals of a Foot for each 1/8 of an Inch To be used in Connection with the Comptometer in Figuring Lumber, Steel Beams, Angles, Etc.
Comptometer Co., Chicago
Form No. 386
152mm × 253mm

This card carries a copyright year of 1925, but it must have been a reprint from the 1940s as it has a picture of the model M.

Ounces and Drams Reduced to Decimal of a Pound Table of Decimal Equivalents to be used in connection with the COMPTOMETER
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 3
253mm × 192mm

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

WAGES TABLE FOR 48-HOUR WEEK To be used in connection with the Comptometer
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 5
304mm × 178mm

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

For Calculating TIMBER SPECIFICATIONS Table to be used in connection with the COMPTOMETER
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 6
354mm × 240mm

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.
It is stamped with the name of the company that used it, W.H. Wheeler & Sons, Portsmouth.

For Calculating the Weight of Deals, Battens, and Boards at 66 cubic feet to the Ton Table of Decimal Equivalents to be used in connection with the COMPTOMETER
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 7
228mm × 240mm

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

GROSS, Each Fractional Part & each 144th To be used in connection with the COMPTOMETER. For Figuring Gross Invoices, Inventories, Plate Glass, etc.
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 8
209mm × 260mm (1925), 203mm × 256mm (1934)

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

This is a later print of the same table. It has a picture of the Model K so probably dates from about 1934.

Decimal Part of a Year for Each Day on a 365-Day Basis To be used in connection with the COMPTOMETER
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 9
184mm × 360mm

This piece of paper has a copyright year of 1914, though it was printed at a later date. From the dates used in the examples printed on the back I suspect it is from 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

Annas & Pies as Decimal of One Rupee Table of Decimal Equivalents to be used in connection with the COMPTOMETER
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 10
328mm × 211mm

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

QRS. & LBS. into CWT. and QRS. & LBS. into TON To be used in connection with the COMPTOMETER
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 21, Dec. Card No. 22
151mm × 239mm (1925), 164mm × 264mm (1934)

This piece of paper has no copyright year, but it has a picture of the Model H or J, and I suspect it is from about 1928. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

This is a later print of the above tables. It has a picture of the Model K so it is probably from about 1934.

Decimal Equivalents of Common Fractions To be used in Connection with the Comptometer.
FELT & TARRANT LTD., Aldwych House, Aldwych, London, W.C. 2.
Dec. Card No. 29
127mm × 203mm

This card has no copyright year, but I suspect it is from about 1928. It is printed by the UK company. It has a list of useful conversion factors on the back.

Pence & Sixteenths of One Shilling and Pence & Thirty-Seconds of One Shilling To be used in connection with the COMPTOMETER
Felt & Tarrant, Ltd., London.
267mm × 209mm

This piece of paper has no copyright year but probably dates from 1934. It is printed by the UK company, and lists the various Felt & Tarrant branch offices around the country.

## Comptometer News magazine

Comptometer News.
Published now and then for Comptometer Operators throughout the World
Frank T. Hess, Editor
1926-19??
32-36 page stapled magazine
153mm × 225mm (Vol I), 153mm × 230mm (Vol III-VIII)

This is a magazine aimed at the operators of the Comptometer, who were mostly young women. It contains mostly office gossip, birth and marriage announcements, and success stories. It gives a fascinating view on the society of the time.

The magazine appeared approximately 4 times a year, from December 1926 until at least 1938. I do not know when it ended its publication, but the copyright was renewed in 1948 so maybe it was still being published then or the company had plans to restart publication.

 Comptometer News, Volume I, Number 1, December 1926, 32 pages (PDF, 11.6 MB) Comptometer News, Volume I, Number 2, February 1927, 32 pages (PDF, 13.4 MB) Comptometer News, Volume I, Number 3, June 1927, 32 pages (PDF, 15.0 MB) Comptometer News, Volume I, Number 4, September 1927, 32 pages (PDF, 13.4 MB) Comptometer News, Volume III, Number 1, January 1929, 36 pages (PDF, 17.0 MB) Comptometer News, Volume III, Number 2, April 1929, 32 pages (PDF, 14.8 MB) Comptometer News, Volume III, Number 3, July 1929, 32 pages (PDF, 14.0 MB) Comptometer News, Volume III, Number 4, October 1929, 32 pages (PDF, 14.5 MB) Comptometer News, Volume IV, Number 1, February 1930, 36 pages (PDF, 17.0 MB) Comptometer News, Volume IV, Number 2, April 1930, 32 pages (PDF, 13.5 MB) Comptometer News, Volume IV, Number 3, September 1930, 32 pages (PDF, 14.4 MB) Comptometer News, Volume VIII, Number 1, February 1936, 36 pages (PDF, 16.2 MB) Comptometer News, Volume VIII, Number 3, October 1936, 36 pages (PDF, 17.3 MB) Comptometer News, Volume X, Number 1, Winter 1938, 36 pages (PDF, 18.0 MB)

Supplements were added to the Comptometer News magazine to cater to specific regions. Shown here is the Australian Supplement that was added to the issues from volume 3 & 4 of the magazine. There were UK supplements too.

 Comptometer News Australian Supplement, Volume 1, Number 3, July 1929, 4 pages (PDF, 2.2 MB) Comptometer News Australian Supplement, Volume 1, Number 4, August 1929, 6 pages (PDF, 3.0 MB) Comptometer News Australian Supplement, Volume 1, Number 5, December 1929, 6 pages (PDF, 3.1 MB) Comptometer News Australian Supplement, Volume 1, Number 6, July 1930, 6 pages (PDF, 3.0 MB) Comptometer News Australian Supplement, Volume 2, Number 1, February 1931, 4 pages (PDF, 2.1 MB) Comptometer News Australian Supplement, Volume 2, Number 2, April 1931, 4 pages (PDF, 1.9 MB)

The Comptometer News supplement for the UK was called "British Brevities". The second one here includes the reply card for the Christmas dinner invitation.

 "British Brevities" of the Comptometer News, Number 8, March 1930, 8 pages (PDF, 3.8 MB) "British Brevities" of the Comptometer News, Number 10, October 1930, 16 pages (PDF, 7.1 MB)

This is the envelope that was used for sending the Comptometer News in, in particular the February 1936 issue. Note that even this envelope is marked with its own publication number, FORM 523.

There are too items to list here, so I have put them on a separate Comptometer Advertisements, Booklets, Leaflets, and Letters page.

## Newspaper Articles

I don't own any physical copies of Comptometer newspaper articles. I have however found quite a few interesting articles in online newspaper and magazine archives. There are too many to list here, so I have put them on a separate Comptometer Articles page.

## Paraphernalia

There are too many paraphernalia to list here, so I have put them on a separate Comptometer Paraphernalia page.

## Patents

The Felt & Tarrant company, and Dorr Felt in particular, filed a lot of patents for all aspects of their inventions and designs. Below is a list of those that relate to the shoebox Comptometer. I have omitted from this list all patents for their other office machines, as well as patents for motorized or powered versions of the Comptometer. Some of the patents listed were never used in any production models, or used only for a short time on some models prior to the model F. The most important ones are displayed in bold type.

PatentFiling datePublish dateNameDescription
US 371,496 12 Mar 1887 11 Oct 1887 Dorr E. Felt First version of the Comptometer, which had a wooden case.
US 568,021 14 Jun 1895 22 Sep 1896 Dorr E. Felt Comptograph
US 661,121 2 May 1898 6 Nov 1900 Dorr E. Felt Comptograph improvements.
US 671,109 24 Oct 1900 2 Apr 1901 Dorr E. Felt Comptometer adapted for Sterling currency
US 733,379 3 Nov 1902 14 Jul 1903 Dorr E. Felt Case lining to reduce sound. Presumably used in Model A.
US 762,520 29 Jun 1903 14 Jun 1904 Dorr E. Felt Improved mechanism to reduce force needed. Presumably used in Model A.
US 762,521 29 Jun 1903 14 Jun 1904 Dorr E. Felt Improved register. Presumably used in Model A.
US 767,107 3 Aug 1903 9 Aug 1904 Dorr E. Felt New clearing mechanism. Presumably used in Model A.
US 960,528 16 Sep 1908 7 Jun 1910 Dorr E. Felt Improved mechanism. Adds carry-blocking buttons. Used in Model B.
US 982,416 4 Apr 1910 24 Jan 1911 Dorr E. Felt Mechanism to detect buttons pressed accidentally. Used later in Model E.
US 982,417 22 Aug 1910 24 Jan 1911 Dorr Eugene Felt Mechanism to detect buttons pressed accidentally. Used later in Model E.
US 992,950 18 Dec 1909 23 May 1911 Dorr E. Felt Mechanism to signal partial key stroke, via column indicator and bell.
US 996,009 4 Mar 1910 20 Jun 1911 Dorr E. Felt Improved carry to reduce key force needed. Presumably introduced in Model C-Light.
US 1,003,723 6 Jan 1911 19 Sep 1911 Dorr E. Felt Improved key-action (heavy to start, lighter through the down-stroke). Presumably used in the Model C-Light.
US 1,028,344 25 Nov 1911 4 Jun 1912 Dorr E. Felt Controlled-key mechanism, locking other keys after partial key stroke.
US 1,066,096 12 Jul 1912 1 Jul 1913 Dorr E. Felt Improved controlled-key mechanism, not releasing partially pressed key until fully pressed.
US 1,072,933 5 Apr 1913 9 Sep 1913 Dorr E. Felt Complete controlled-key mechanism.
US 1,072,934 5 Apr 1913 9 Sep 1913 Dorr E. Felt Improved clearing mechanism, reduced jamming with improper use.
US 1,074,689 30 Sep 1912 7 Oct 1913 George Steninger Bollensen Keyboard with a fractions column
US 1,074,704 5 Apr 1913 7 Oct 1913 Dorr E. Felt Keyboard with several columns for common fractions
US 1,074,705 5 Apr 1913 7 Oct 1913 Dorr E. Felt More reliable clearing mechanism
US 1,110,734 3 Mar 1914 15 Sep 1914 Kurt F. Ziehm New Controlled-Key mechanism. Presumably introduced in the Model F.
US 1,154,897 9 Oct 1911 28 Sep 1915 Joseph Abram Turck Improved mechanism to reduce key force needed.
US 1,357,747 1 May 1918 2 Nov 1920 Joseph A. V. Turck New clearing mechanism. Introduced in Model H.
US 1,357,748 1 Dec 1919 2 Nov 1920 Joseph A. V. Turck Improvement on the new clearing mechanism, with bell. Introduced in Model H.
US 1,391,220 24 Apr 1920 20 Sep 1921 Joseph A. V. Turck Early version of the Super Totalizer.
US 1,449,639 19 May 1921 27 May 1923 Joseph A. V. Turck Controlled-key mechanism that also locks clearing lever.
US 1,714,964 12 Mar 1921 28 May 1929 Joseph A. V. Turck Column indicator for controlled-key mechanism.
US 1,751,609 8 Oct 1923 25 Mar 1930 Joseph A. V. Turck Block clearing handle when controlled-key mechanism active.
US 1,817,640 30 Apr 1929 04 Aug 1931 Neal Eberhart Newman; Frederick Adolph Niemann Peg-Board system.
US 1,840,378 27 Oct 1926 12 Jan 1932 Carlos Wittenmyer Carry blocking levers that are automatically released by carry.
US 1,902,597 29 Sep 1927 21 Mar 1933 Joseph A. V. Turck More reliable clearing mechanism. Presumably introduced in Model J.
US 1,927,856 29 Sep 1927 26 Sep 1933 Joseph A. V. Turck Operator-controlled locking of key columns and digits.
US 2,104,051 16 May 1935 4 Jan 1938 Frederick A. Niemann Super Totalizer digit blinds.
US 2,130,364 5 Nov 1934 20 Sep 1938 Frederick A. Niemann Super Totalizer.
US 2,149,817 5 Nov 1934 7 Mar 1939 Frederick A. Niemann Super Totalizer.
USD 113,817 26 Aug 1938 14 Mar 1939 Frederick A. Niemann, Alfred L. Mell Model M case design.
US 2,273,491 28 Apr 1939 17 Feb 1942 Haldon A. Leedy Vibration proofing mounting of mechanism and case
US 2,346,601 24 Feb 1941 11 Apr 1944 Frederick A. Niemann Hide leading zeroes
US 2,753,117 22 Sep 1954 3 Jun 1956 Emil C. Walker Customatic mechanism