My Mechanical Calculators
This page is devoted to my small collection of (mostly) mechanical calculators.
If you have comments, you can contact me (Jaap Scherphuis) at
mechcalc a t jaapsch d o t net.
On the left you can filter the list of calculators by selecting only the categories that you want to see.
An explanation of these categories is on a separate page.
Addimat
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This is an Addimat, probably from about 1962-1963. In Europe they were renamed Addipresto in 1964.
It is in good working condition, with stylus and protective cover. Simply enter the numbers to add with the stylus, and the result is shown in the register. When a digit overflows, it carries automatically to the next digit. The red lever zeroes the digits. It was made in Italy, and in production from 1955 to about 1970. More information on the Addimat. |
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This is a Schnellrechner, from about 1970.
It is an exact copy of the Addimat / Addipresto. It was made in Hong Kong, and in production from about 1965 to 1975. More information on the Schnellrechner. |
Aderes
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This is an Aderes column adder, without serial number, unknown year of production.
It is in excellent working condition. The Aderes is a version of the Adix, invented by Joseph Pallweber, first made in 1903. Versions of the Adix with bakelite cases were made from the 1920s or 1930s all the way into the 1950s. More information on the Aderes. |
Alexe
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This is the Alexe Mini Calculator. It has no serial number.
It can add and subtract, and is in working condition except that the clearing mechanism fails to clear the tens digit. The Alexe was invented by Masaharu Nara around 1965 and was made by Meiwa or Ricoh in Japan in the late 1960s. More information on the Alexe. |
Anita
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This is the Anita 811. It has no serial number.
It is an early electronic pocket calculator, comes with a leather case, and is in working condition. The Anita 811 was made by Sumlock Comptometer Ltd. (a subsidiary of Bell Punch) in 1972. More information on the Anita 811 and other Bell Punch machines. |
Benton Tally Register
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This is a hand tally register, probably made by Benton Mfg. Co. from New York.
It has a 3-digit counter that increments when you push the button. It has no serial number. It was in production from 1884 till at least 1963 with hardly any change in design. More information on the Benton Tally Register. |
The British Calculator
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The British Calculator was made by T.J. Marshall & Co in Stoke Newington, London.
Its register handles British currency values up to £500. It has serial number 1681. It was in production from 1906 until about 1914. More information on The British Calculator. |
Brunsviga
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The Brunsviga Nova II was made by Grimme, Natalis & Co in Brunswick, Germany.
It is a pinwheel calculator that has its revolution counter built into the main body above instead of in the carriage. It also has a back transfer mechanism. It has serial number 6T 2O 864. It was in production from 1925 until 1934. More information on Brunsviga Nova II. |
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The Brunsviga 90 TA was made by Siegfried Link for Brunsviga.
It is an adding machine with a toothed rack mechanism. It has serial number 22-05788. It was in production from 1956 until 1959. More information on Brunsviga 90 TA. |
Burroughs Calculator
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This is a Burroughs Calculator, shoebox model, serial number 206979.
It is a key-driven calculator, deliberately styled to be very similar to the Comptometer by Felt & Tarrant. This version was made by the Burroughs Adding Machine Company from 1911 until at the latest 1915, when the court case brought by Felt & Tarrant forced Burroughs to change the design. |
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This is the redesigned Burroughs Calculator, serial number 5-572171. This version was made by the from 1915 until about 1935s, at which time the case was redesigned. |
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This is a 6-digit "Baby" Burroughs Calculator, serial number A720100. This version was made by the Burroughs Adding Machine Company from 1928 until the 1960s, but this particular one is probably from the 1940s. |
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This special edition "Baby" Burroughs Calculator is pink,
and has an A monogram on the front. It was made as a gift for Princess Anne and presented to Queen Elizabeth II and Prince Philip when they visited the Burroughs factory in Strathleven, Scotland. More information on the Burroughs Calculators. Burroughs Advertisements, from various online newspapers, magazines, and other sources. Burroughs Articles, from various online newspapers, magazines, and other sources. |
Calcumeter
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This is a Standard Desk Calcumeter, serial number (99)89158, from about 1912.
It is a rotary adder, in good working order, but without stylus. It was made in the USA from 1903 to about 1914. More information on The Standard Desk Calcumeter. |
The Checkbook Balancer
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This is The Checkbook Balancer.
It is a small rotary adder, with stylus, designed to fit inside an American checkbook. It was made in around 1970. More information on The Checkbook Balancer. |
Comptometer
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This is a Comptometer, a 12-column Model E with serial number 56337, from 1913 or 1914.
The left key column is stuck but otherwise it works normally. The Controlled-Key release should be a white button instead of the red one that was used on all later models. |
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This is a 10-column Model J Comptometer, serial number J314420, from about 1934.
The cosmetic condition of its case is rather poor, but it works perfectly. It was reconditioned in the 1950s, during which its case was wrinkle painted green, and its keytops replaced. |
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This Comptometer is a model J Super Totalizer, serial number J317903 / S1415, from about 1934.
It is in very good working condition, but has had some restoration done. In particular, 9 of the key tops are later reproductions, and the celluloid windows have been replaced with modern plastic. |
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This Comptometer is another model J Super Totalizer, serial number J345247 / S3150, from 1937 or 1938.
It is in rather poor condition, but could be used for spares. The most interesting thing about this one is its very late model number, possibly one of the last 2000 model J's ever made. The Comptometer was invented in 1886 by Dorr E. Felt, and made by Felt & Tarrant in Chicago, USA, until 1961. More information on the Comptometer, including several books, manuals, and other paraphernalia related to the Comptometer and Felt & Tarrant. Comptometer Advertisements, from various online newspapers, magazines, and other sources. Comptometer Articles, from various online newspapers, magazines, and other sources. Mechanical Arithmetic, or, The History of the Counting Machine, a lecture about calculators by Dorr Felt which was published in 1916. |
Contex
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This is the Contex B made by the Brothers Carlsen.
It is a simple half-keyboard adder, with a 9 digit register. It has serial number 537817. This model was made in Denmark from 1951 to 1970, though mine is from before 1961. |
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This is the Contex 10 made by the Brothers Carlsen.
It is a cleverly designed 10-key mechanical calculator, with an 11 digit register. It has serial number 434 077240. This model was made in Denmark between 1957 and 1971, though mine was made after 1963. More information on the Contex machines. |
Conto
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This is a Conto model C adder, with serial number 2578, possibly made around 1930.
The Conto was made in Switzerland. The first model was invented by Karl Karasek and Johannes Aumund in 1906. Carl Landolt produced the model B and then the model C until his death in 1923, and the last model Cs were made around 1932 by Alfred Müller. More information on the Conto. |
Corema
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This is the Corema Portative MC 15.
It has an 8-digit display and an 8-column full keyboard. It has serial number 23128. It was made in Geneva, Switzerland from 1952 until the 1960s. More information on the Corema Portative MC 15. |
Curta
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This is a Curta Type I, serial number 57064, from 1964.
It is in good working condition, but the clearing ring has a crack on one side. It comes in a protective metal case which has a quite a lot of wear. The two booklets are modern reproductions of the originals, "Instructions for use of the CURTA" and "Computing Examples for the CURTA Calculating Machine". The Curta was invented by Curt Herzstark, and made by Contina AG Mauren, based in Mauren, Liechtenstein. It was in production from 1948 to 1972. More information on the Curta. |
Denominator Lab Counter
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This is a lab counter made by the Denominator Company.
It has five independent 3-digit counters and a 3-digit totaliser counter. It has serial number 25029. It was made in the USA in 1948. More information on the Denominator Lab Counter. |
Dial-A-Matic
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This is a Dial-A-Matic, a rotary adder made by Sterling Plastics Co.
It was made in the USA from 1955 to about 1970. |
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This is the SEE "calculator", a transparent version of the Dial-A-Matic, made by Sterling for Selective Educational Equipment Inc.
It was made in the USA from 1968. More information on the Dial-A-Matic and the See Calculator. |
Direct
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This is the Direct II calculator, made by Moesch & Huber, distributed by Theo Muggli.
It has a 10-digit display, and a 10-digit internal result register. It has serial number 26509. It was made in Switzerland from the late 1920s until the 1940s or 1950s. More information on the Direct II. |
Facit
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This is a Facit C1-13.
It is a pinwheel calculator from 1957, which uses a 10-key keyboard for input. It has serial number 556,853. Versions of this machine were made in Sweden from 1932 until 1969. More information on the Facit C1-13. |
Golden Gem
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This is a Golden Gem.
It is a small chain adder from 1912, with stylus and leather case. It has serial number 48988. It was made in the USA from 1906 until at least the 1930s. More information on the Golden Gem. |
Hamann
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This is a Hamann Manus.
It looks like a pinwheel machine, but it uses the latched gear mechanism invented by Christel Hamann. It has serial number 15421. It was made in Germany from 1925 until 1955, with small variations over time. More information on the Hamann Manus. |
Kes-Add Pocket Adder
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This is a Kes-Add Precision Pocket Adder.
It is a small rotary adder, with stylus. There is no serial number. It was made in the USA in the 1950s. More information on the Kes-Add Precision Pocket Adder. |
Lightning Adding Machine
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This is a Lightning Adding Machine, made in Los Angeles, USA, in February 1946.
It is a rotary adder, in good working order, with aluminium stylus and Bakelite stand. This version was in production from October 1945 to 1950. |
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This is a Lightning Adding Machine, made in Los Angeles, USA, in about 1953.
It has a clearing lever, and comes with aluminium stylus, Bakelite stand and instructions. This version was in production from 1950 to about 1959. More information on The Lightning Adding Machine. |
Marchant
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This is a Marchant XL, serial number XL100215.
It is a hand-cranked mechanical calculator based on the adapting segment mechanism designed by Carl Friden. The model XL was made by the Marchant Calculating Machine Company from 1923 to about 1935. More information on the Marchant machines. Marchant Advertisements, from various online newspapers, magazines, and other sources. Marchant Articles, from various online newspapers, magazines, and other sources. |
Minerva
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The Minerva was made Olympia-Brunsviga and manufactured in Spain. Minerva was the brand used in Spain, while in most other countries this is the Olympia-Brunsviga 13 RM.
It is a pinwheel calculator with back transfer mechanism. It has serial number 30091. More information on the Minerva. |
Monroe
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This is a Monroe model K, serial number K160-144100.
It is a manual calculator using a split stepped drum mechanism. It is in excellent condition. The model K was made by the Monroe Calculating Machine Company from 1921 to about 1929. |
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This is a Monroe model KA, serial number KA160-129883.
It is the electrically driven version of the model K. All the electric wiring needs to be replaced, but other than that most of the mechanism is in working order. |
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This is a Monroe model L, serial number L-200X-228247.
It is the successor to the model K, and virtually the same except half-sized. Variants of the model L were made from 1930 until the 1960s. More information on the Monroe machines. Monroe Advertisements, from various online newspapers, magazines, and other sources. |
Peter Pan Adding Machine
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This is the Peter Pan Adding Machine.
It is toy adder, with sliders that can me moved with your finger instead of a stylus. It is made of tin plate sheets. There is no serial number. It was made in the early 1950s in England. It is a licensed copy of the Wolverine Adding Machine made at the same time in the USA. More information on the Peter Pan Adding Machine. |
Plus Adder
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This is a Plus Adder, model 506/C, serial number 45953, from about 1950.
It is in good working condition, except that one of the key tops is missling. The Plus Adder was made by Bell Punch, a British company that was based in Uxbridge, from 1939 to the late 1960s. |
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This is a Plus Adder, model 509/C, serial number 824523, from about 1960.
It mostly works, except that one of the plastic gears that controls the left-most digit is missing some teeth. |
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This is an adder of unknown origin and purpose, but its mechanism is taken from a Bell Punch Plus Adder.
Its clearing mechanism can also be triggered electrically. More information on the Bell Punch machines. |
Pocket Adding Machine
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This is The Pocket Adding Machine.
It is small slide adder, with stylus, and housed in a fake alligator skin case. There is no serial number. It was made in the early 1920s. More information on The Pocket Adding Machine. |
Pocket Counter
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This is The Pocket Counter.
It is small push-button adder, made of red plastic with white buttons. There is no serial number. It was made in Japan in the 1960s or 1970s, especially for the American market. More information on The Pocket Counter. |
Rapid Computer
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This is a Rapid Computer.
It is a small toothed rack adder from about 1907, with stylus and box. It has serial number 3198. It was made in the USA from 1905 until about 1915, and was the basis for the Comptator made in Germany. More information on the Rapid Computer. |
Resulta
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This is the Resulta E7.
It is small adding/subtracting machine. There is no serial number but a date of July 1963. Versions of this machine were made in Berlin from 1927 to 1969. More information on the Resulta E7. |
Seidel & Naumann
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This is the SuN adder by Seidel & Naumann.
It is a small chain adder, with stylus and storage box, and has serial number 10451. It was made in Germany from about 1910 until the early 1920s. More information on the Seidel & Naumann adder. |
Slide Rule
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This is a plastic slide rule by Hemmi, model P40RK, with the date stamp "T H" which means it is from August 1969.
It has the following scales: C and D (multiplication/division), CI (reciprocals) A and B (squares, square roots), K (cubes, cube roots), and on the reverse S (sines, cosines), L (base 10 logarithms), T (tangent, cotangent). It was made in Japan. This exact model was in production from 1967 to 1969, but Hemmi made slide rules from 1913 to 1975. |
Stephenson's Adder
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This is a second generation Stephenson Adder, in good condition. There is no serial number, and on the back it says "A.M. Stephenson / Mfr, Joliet Ill. / Agents wanted".
It was probably made between 1896 and 1910.
The first generation of this popular small adder was made in the 1870s. |
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This is clone of the Stephenson Adder, which was probably made between 1910 and 1915 and sold by the name Perfection Adding Machine. On the back it says "Cin. Specialty Mfg. Co. / Cincinnati, O".
More information on Stephenson's Adder. |
Stima
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This is the Stima adder, invented by Albert Steinmann.
It is a slide adder, encased in a Bakelite case for desk use. It has serial number 19458. It was made in Switzerland from about 1930 until the at least the late 1940s. More information on the Stima adder. |
Sumlock
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This is a Sumlock, model 909/D, serial number 41440, from the early 1940s.
It is in working condition, though one of the keys tends to stick. |
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This is a Sumlock, model 906/C, serial number 103629, from the 1940s.
It is in working condition. The Sumlock was made by Bell Punch, a British company that was based in Uxbridge, from 1940 to the late 1960s. More information on the Bell Punch machines. |
Thales
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This is a Thales KA, serial number 39507, from about 1960.
It is in fairly good working condition. It was made in West Germany and in production approximately from 1953 to 1963. More information on the Thales KA. |
Triumphator
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This is a Triumphator KA, serial number 15615, from about 1960.
It is in perfect condition. It was made in East Germany and in production approximately from 1958 to 1960. More information on the Triumphator KA. |
Unitas
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This is a Unitas calculator, serial number 03117/2014, possibly from about 1912.
It is a stepped drum calculator in good working condition. It is missing a few decimal indicators, and one of the four knobs that locks the front panel in place. It comes with a protective cover which is in poor conidition. It was in production from 1907 to about 1941. More information on the Unitas calculator. |
Walther
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This is a Walther RMKZ, serial number 10890, possibly from about 1933.
It is in fairly good working condition. The part of the body holding the crank handle has cracked. At some point, possibly in the 1950s, it has been changed from its original black paint to this metallic hammer grey enamel. It was in production from the early 1930s to 1952. More information on the Walther. |
The Webb Adder
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This is a second generation Webb Adder, in good condition. There is no serial number and no writing on it.
It was probably made in around 1900 or 1910.
The first generation of this popular small adder was made in 1869, and the second generation was manufactured from 1890 onwards. More information on the Webb Adder. |
Links
Rechenmaschinen illustrated
Rechner lexikon
Jay M. Goldman
John Wolff
Cris vande Velde
National Museum of American History
History of Computers
Rechnen ohne Strom - "Calculation without electricity" in German.
Original Documents on the History of Calculators by Andries de Man.
Revision History
2019-09-18: Added a page about how to classify machines and mechanisms, and implemented filter functionality in the main page.
2019-09-16: Added two Monroe calculators, models K and L, with a video, and expanded the page.
2019-09-12: Added The Story of Figures, a promotional booklet by Burroughs.
2019-09-07: Added a later model of Lightning Adding Machine that has a clearing lever and instructions.
2019-09-02: Added a card recruiting Comptometer School students. Added a Dutch Comptometer letter from 1919. Added another Comptometer medal. Added more information and articles about the Benton tally register.
2019-09-02: Added a new page about the Dial-A-Matic and the SEE Calculator.
2019-08-18: Added the Addimat, of which the Schnellrechner is a clone, with a video.
2019-08-14: Added the German manual for the Hamann Manus calculator.
2019-07-28: Added a new page about the Hamann Manus calculator.
2019-07-21: Added a metal box dust cover for the Comptometer.
2019-07-17: Added a postcard from 1895 offering a free trial of the Comptometer.
2019-07-07: Added pictures of more Comptometer Medley issues and the UK edition of Comptometer News (now all housed on a separate page). Added another Comptometer Reunion programme and a celluloid Comptometer Calendar.
2019-06-21: Added the Brunsviga 90 TA adding machine.
2019-06-10: Added a new page about the Triumphator KA Adding Machine.
2019-05-30: Added a new page about The Checkbook Balancer.
Added the Operating Instructions for Marchant Calculators.
Added another Plus adder by Bell Punch.
2019-05-12: Added a new page about the Peter Pan Adding Machine.
2019-04-19: Added a new page about the Conto calculator.
2019-04-14: Added a new page about Marchant calculators, in particular the Marchant XL, with a page of Marchant advertisements and a page of Marchant articles.
2019-03-11: Added a 1920s era Burroughs Calculator to the Burroughs page, with a comparison video.
2019-03-09: Added a new page about Stephenson's Adder.
2019-02-11: Added a new page about the Brunsviga Nova II, and the Minerva.
2019-01-15: Added a manual for the FACIT CS1-13 as well as several flyers for various FACIT models, added a flyer for the Resulta AS, added an instruction leaflet and guarantee for the Thales KA, added a leaflet for the Plus adder.
2019-01-09: Added a Burroughs keychain.
2018-12-24: Added the 1921 edition of the "Methods of Operating the Comptometer".
2018-12-23: Added the 1963 edition of the "Comptometer Course for Business Training", together with its Answer Book and Review Tests.
Added the "Handbook of Instruction for Operators of the Burroughs Adding and Listing Machines" from 1911, and split off the Burroughs books to a separate page.
2018-12-16: Added a new page for the Rapid Computer. Added "Rule for Extracting Cube Root with the Comptometer".
2018-12-08: Added some Adix advertisements to the Aderes page.
2018-12-02: Added a separate page for the many Monroe advertisements from newspapers and magazines.
2018-11-22: Added the book "Short-cut calculations with FACIT".
2018-11-16: Added many more Burroughs advertisements from Finnish newspapers.
2018-11-13: Added a page with newspaper and magazine articles about Burroughs.
2018-11-12: Added a normal Baby Burroughs Calculator, a very special Princess Anne Baby Burroughs Calculator, and expanded the page further.
2018-10-16: Added another version of the Diploma Course Operators Notebook.
2018-10-09: Added pictures and pdf scan of the Answer Book to Manual of Instruction for Burroughs Calculator.
2018-10-06: Added some Facit keychains.
2018-09-30: Added the Stima adder.
2018-09-25: Added a postcard depicting the Comptometer Commander dictation machine.
2018-09-16: Added the "Answer Book for the Comptometer Course for Business Training".
2018-09-11: Added the 1953 issue of the Comptometer Medley magazine.
2018-09-02: Added a new page on The British Calculator.
2018-08-21: Added the pdf scan of the Italian version of "Easy Instructions for operating the Controlled-Key Comptometer"
2018-08-19: Added another version of the Diploma Course Operators Notebook.
2018-08-11: Added a new page on the Benton Tally Register.
2018-08-07: Added a new page on the Unitas stepped drum calculator.
2018-06-03: Added a new page on the Seidel & Naumann chain adder.
2018-05-14: Added a new page on the Corema Portative MC 15.
2018-03-23: Added a Burroughs School certificate.
2018-03-17: Added two standard letters that Felt & Tarrant sent to Lamson & Goodnow.
2018-03-10: Added a Burroughs cigarette lighter.
2018-02-04: Added a Comptometer Training School badge and a Comptometer patch from a uniform.
2018-01-07: Added a video of the Curta calculator.
2018-01-01: Added an Italian version of "Easy Instructions for operating the Controlled-Key Comptometer",
added the instruction leaflet to the Comptometer Dictation machine,
added various mostly Italian Comptometer advertising leaflets,
added a collection of Italian Comptometer photographs.
2017-12-23: Added a new page about the Webb Adder.
2017-12-02: Added a new page on the Direct II.
2017-11-21: Added the 1930 version of "Easy Instructions for operating the Controlled-Key Comptometer", and split off the books to a separate page.
2017-11-18: Added a new page about the Thales KA.
2017-11-12: Added a new page about the Contex B and Contex 10 calculators.
2017-11-08: Added a San Francisco newspaper photograph of a Comptometer world record holder.
2017-09-28: Added a 1934 postcard of the Comptometer school at Aldwych House in London.
2017-08-16: Added the Curta Square Root Tables.
2017-08-11: Added the 1928 manual "Instructions for Operating the Burroughs Calculator".
2017-08-07: Added two promotional cards for the Comptometer.
2017-07-30: Added a new page on the Facit C1-13, a pinwheel calculator with 10-key keyboard.
2017-07-23: Added the scanned pdf version of the French manual "Instructions pour utiliser la Burroughs Calculator".
2017-07-21: Added the promo book "Helping Ford Handle his Millions".
2017-07-16: Added a video of the Walther RMKZ.
2017-07-06: Added the 1915 version of "Easy Instructions for operating the Comptometer".
2017-07-05: Added a green enamelled Sumlock badge.
2017-07-02: Added a new page on the Resulta E7.
2017-06-12: Added "Decimal Equivalent Tables", a bound collection of tables for the Burroughs calculator.
2017-05-12: Added a Comptometer School certificate.
2017-05-07: Added a new page on the Golden Gem chain adder.
2017-04-27: Added a new page on the Denominator Lab Counter.
2017-04-17: Added a video of the Alexe Mini Calculator.
2017-04-14: Added a 1929 brochure for Burroughs machines.
2017-03-29: Added a Swedish promotional card for the Comptometer.
2017-03-26: Added a new page on the Lightning Adding Machine.
2017-03-11: Added a new page on the Calcumeter. Added a Comptometer School Diploma.
2017-03-05: Added 85 Comptometer adverts, mostly from the Scientific American and the Literary Digest.
2017-02-26: Added various newspaper and magazine ads for various Bell Punch and Sumlock calculators.
2017-02-08: Added two Sumlock Charts books of tables.
2017-01-27: Added pictures of the Courtesy Course for the Comptometer, and of a repeat customers list with the Stop To Think booklet.
2017-01-22: Added many Comptometer leaflets and letters, as well as a hat pin, two more badges, and an oil bottle.
2017-01-02: Added a new page of Burroughs advertisements taken from online newspaper and magazine archives.
2017-01-01: Added the book "Cheer Up and 52 Reasons Why" to the Burroughs page.
2016-12-17: Added the book "A Better Day's Work" to the Burroughs page.
2016-12-14: Added the "Stop to Think" advertising booklet to the Comptometer page.
2016-12-09: Added the (Sumlock) Operators Notebook Basic Course.
2016-12-08: Added two "British Brevities" supplements to the Comptometer News magazine.
2016-12-07: Added the Anita 811.
2016-12-06: Added the Winter 1938 issue of Comptometer News (No. 1 Vol. X).
2016-12-05: Added the September 1930 issue of Comptometer News (No. 3 Vol. IV).
2016-12-04: Added a new page for the Burroughs Calculator.
2016-12-03: Added the 1928 edition of Methods of Operating the Comptometer.
2016-11-27: Added a video of my Model E Comptometer.
2016-11-21: Replaced the pdf for the February 1930 issue of Comptometer News (No. 1 Vol. IV) to add missing pages.
2016-11-17: Added pictures of my Model E Comptometer.
2016-10-30: Added the Comptometer pages from the Kantoormachine Gids.
2016-10-29: Added A Great Step Forward, a promotional booklet for the Comptometer.
2016-09-30: Added the 1958 edition of Easy Instructions for operating the Accuracy Key Comptometer.
2016-09-28: Added New Zealand Comptometer adverts and a few Dutch ones. Added some Comptometer newspaper articles from New Zealand.
2016-09-25: Added many Monroe adverts. Added many Comptometer newspaper articles. Added several Comptometer adverts (UK, USA, Netherlands).
2016-09-23: Added several Finnish Comptometer adverts. Added a few Finnish Comptometer newspaper articles.
2016-09-19: Added three Comptometer adverts found on eBay.
2016-09-17: Added several Comptometer tables and an advertising leaflet.
2016-09-15: Added newspaper articles about the inventor of the Kes-Add.
2016-09-14: Added a video of the Kes-Add.
2016-09-13: Added a video of The Pocket Counter.
2016-09-12: Added a video of The Pocket Adding Machine.
2016-09-11: Added a new page on the Schnellrechner.
2016-09-10: Added a new page on the Pocket Counter.
2016-09-09: Added a new page on the Kes-Add Pocket Adder.
2016-09-08: Added a new page on the Alexe Mini Calculator.
2016-07-19: Added a new page on The Pocket Adding Machine.
2016-07-13: Added a Sumlock ready reckoner disk.
2016-07-05: Added a Comptometer medal to the paraphernalia section.
2016-07-02: Added an unknown custom variant of the Bell Punch adder.
2016-06-25: Added two Monroe booklets about extracting square roots and higher roots.
2016-06-22: Added a third Comptometer badge to the paraphernalia section.
2016-06-21: Added many advertisements for the Monroe, mostly from Life magazine.
2016-06-05: Added pdf of Chester H. Katenkamp's Office Machine Practice book for The Monroe Calculating Machine.
2016-06-04: Added the (Sumlock) Operators Notebook Diploma Course.
2016-06-02: Added pictures of Chester H. Katenkamp's Office Machine Practice book for The Monroe Calculating Machine.
2016-05-30: Added a newspaper article and an advertisement to the Monroe page. Added newspaper advertisements to the Curta page.
2016-05-27: Added a page on the Monroe model K.
2016-05-24: Added a page on the Aderes column adder.
2016-05-20: Added the Instruction Manual for the Operation of the Comptometer, as used in Comptometer schools. Expanded the list of Comptometer patents.
2016-05-18: Added the Operators Notebook, Tables, price list and flyers to the Bell Punch page.
2016-05-15: Added 5 Comptometer articles and book extracts (The Complete Cost-Keeper, Nicholson On Factory Organization and Costs, The Non-Listing Adding Machine and Its Uses, Business Costs, The Accountant's Dictionary)
2016-05-14: Added my reconditioned Model J Comptometer.
2016-05-07: Added some newspaper advertisements.
2016-05-04: Added the page on the Sumlock and Plus Adder by Bell Punch.
2016-04-27: Added the Computer History Museum's Super Totalizer to the list. Added 5 Comptometer ads from 1940-1948 that were found on eBay.
2016-03-24: Added the 1920 edition of "Easy Instructions for operating the Controlled-Key Comptometer".
2016-03-19: Added College Made Utopias and Labor Unrest and a better version of the Mechanical Arithmetic article.
2016-03-10: Added the Adding Practice book, and a pristine version of the manual for the Comptometer Educator.
2016-03-09: Added the javascript Comptometer Simulator.
2016-02-29: Added the 99c "Customatic" Comptometer to the list of models. Added a final set of Comptometer ads from Nation's Business from 1957-62, and a few ads from the ABA (American Bar Association) Journal.
2016-02-26: Added 10 Comptometer ads from Nation's Business from 1956-7, and a few other US ads from various sources.
2016-02-25: Added second edition of the Key-Driven Calculator Course book, and an Italian Comptometer advertising leaflet from around 1900.
2016-02-19: Added the Comptometer articles section on court cases, and a few other articles.
2016-02-17: Added second Comptometer badge.
2016-02-15: Added two 1905 Comptometer advertising postcards, and three paper tables.
2016-02-14: Added several Comptometer articles from the Chicago Tribune such as Felt's obituary. Recategorized the articles.
2016-02-10: Added early Scientific American Comptometer ads and several later ones from System. Added several Comptometer articles form Office Appliances and System.
2016-02-06: Added several early U.S. Comptometer adverts from various newspapers. Added some Comptometer articles from various newspapers.
2016-02-04: Added many more U.S. adverts mostly from the magazines System, Factory, and Business. Added a few Comptometer articles, mostly from the magazines System, Factory, and Business.
2016-02-02: Added scanned pdfs of the "Noiseless Duplex" and "Rapid Mechanical Calculation" promotional Comptometer booklets.
2016-02-01: Added a few more Comptometer adverts, this time from the Independent magazine. Added a few more adverts, this time from the Independent magazine.
2016-01-31: Added the scanned pdf of the "Enforced Accuracy" promotional booklet, and a list of promotional booklet titles at the start of the advertisements section. Added more adverts from Maclean's magazine. Added more Comptometer adverts from Maclean's magazine.
2016-01-30: Added the Key-Driven Calculator Course to the Comptometer books section. Added the Nation's Business adverts, the Dicksee lecture extract, and a few other items. Added the Nation's Business adverts, the Dicksee lecture extract, and a few other items.
2016-01-26: Added pictures of three Comptometer promotional booklets (Noiseless Duplex Comptometer, Rapid Mechanical Calculation, Enforced Accuracy)
2016-01-25: Added three Comptometer promotional leaflets (World's Record at Adding, Waiting Your Instructions, Proof of the Pudding)
2016-01-20: Added an issue of Comptometer News (Volume VIII, Number 1, February 1936) as well as its envelope.
2016-01-11: Added this revision history.
2016-01-10: Added the scanned pdf of the book "How to Use the Calculator and the Comptometer" by James R. Meehan.
2016-01-08: Added the pictures and scan of a Comptometer Reunion Souvenir Programme.
2015-12-23: Added the pictures of a Box of Comptometer Playing Cards.
2015-12-12: Added pictures of the book "How to Use the Calculator and the Comptometer" by James R. Meehan.
2015-11-29: Added pictures and scan of an Italian Comptometer advertising leaflet.
2015-11-25: Added pictures of a Dutch card for Comptometer Model S.
2015-11-19: Added pictures of a gold Comptometer ring.
2015-11-18: Added pictures and scan of the French "Comptometer - Méthode Pour Opérer" booklet.
2015-11-17: Added pictures of a Comptometer postcard.
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