Jaap's Mechanical Calculators Page


The Denominator The Denominator

The Denominator
Denominator Lab Counter

The Denominator

The Denominator is a machine containing 11 separate 3-digit counters. Each counter has a single button with which it can be incremented. The wingnut on the left hand side clears all the counters simultaneously. The buttons are marked with the denominations of US money, from $20 down to 1 cent. A company could use this machine to add up the amounts on all the staff payslips so as to know how much of each denomination was needed to pay out their wages. The Denominator is attached to a wooden base, and the space to the right of the machine used to have a shelf or stand that could hold a stack of payslips.

Note that it has a counter for a 3 cent coin, even though that coin had not been minted in about 25 years when the Denominator was first made. This allowed for the possibility that it would be introduced, and the counter could also simply be used as an extension of the 1 cent counter.

The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator

The serial number is 1940, and can be found on the clearing wingnut. It seems to be fairly rare. I found only three other serial numbers online, which are 2249, 2970, and 3540. If the numbering really started at 1, this suggests that about 4500 Denominators were made. Production started in 1915 but it is not clear when it ended.

The mechanism is very simple. Each button is connected to an actuator piece with three teeth of different lengths. These teeth drive the three number wheels of the counter by engaging with the gear on the left side of each wheel. Usually only the longest tooth of the actuator is engaged with its number wheel so that only the units wheel is incremented. When a wheel is on nine, its gear presents a deeper hole to the actuator causing the latter to dip and letting its next larger tooth connect to the next wheel. At the next increment the next wheel is then incremented too, effecting a carry.

My denominator has seen a lot of use, and has been repaired in order to keep it working. The spring for the actuator on the 1 cent counter is broken, and a new home-made spring has been mounted on top. The 5 cent number wheels have worn out so much that they have become too loose on the axle. To avoid them slipping off the actuator, a small guide has been mounted to keep them in place.

The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator
The Denominator


Denominator Lab Counter

This machine has five independent 3-digit counters, and a totaliser. There are five buttons, one for each counter, and when you press one of them 1 is added to its counter. The button also pushes down a bar that is connected to where the button of the totaliser would be, so that every button press also increments the totaliser. This kind of machine is called a Lab Counter because it can be used when running a laboratory experiment with many samples that can have up to 5 different outcomes. Clips on the front of the counters allow you to insert a label to mark what each counter is being used for.

Each counter unit has a date printed on the bottom. The most legible one is Oct 29 '48, so presumably it was manufactured in 1948 or shortly thereafter. However, the decal on the front uses a logo that according to its trademark application was first used in 1950. This is probably the last generation of fully metal counters they made since the patent filed in 1949 shows their new design that uses a plastic casing. The serial number 25029 is stamped under the edge of the case.

The Denominator
The Denominator, button pressed 1
The Denominator, button pressed 2
The Denominator, logo
The Denominator, label clips
The Denominator, reset nut
The Denominator, rear
The Denominator, bottom
The Denominator, bottom, date close-up
The Denominator, bottom, serial number

To reset the counters, turn the wing nut until all the digits read zero. The wing nut on the left clears the five counters simultaneously, and the wing nut on the right clears only the totaliser. Turning the wing nuts the wrong way has no effect, though it can mean that you have to turn it almost two whole revolutions to clear the counters next time.

The Denominator, interior, front
The Denominator, interior, back 1
The Denominator, interior, back 2
The Denominator, interior, totaliser

The totaliser has a locking mechanism, but it has been disabled. There should be a small pin in the hundreds wheel of the totaliser which would slide the locking bar in place when the wheel turns from 0 to 1. At this point the total is 100, so the numbers in the other counters can be read as percentages of the total. This model does not seem to have had any release mechanism for the lock other than resetting the totaliser counter. I found a patent for such a release mechanism that was filed in 1951.

The machine is in reasonable condition. Some of the wrinkle paint is flaking off, the window of the totaliser counter has been replaced with a yellower plastic, and a spring is broken that should push the totaliser bar back up again after a button press.



The Denominator Adding Machine Company was founded by Frank H. Morse in Brooklyn, New York, in 1914. It was founded in order to produce the Denominator, shown above, which has a separate counter for each denomination of US currency from $20 to 1 cent, and a single reset mechanism. It seems that the patent was not filed until 1921, granted in 1923. It states that the machine was designed by William A. Cook and Joseph Levine, and the patent was signed by Frank Morse as a witness.

The Denominator Adding Machine Company soon found that there was a demand for other kinds of counters, so versions of the denominator were made with plain buttons and a rail to hold a strip of paper for labelling the counters. A small 3-button version was made too.

The company address shown on the earliest denominators was 224-226 Shepherd Ave., Brooklyn, New York. They shared this factory building with the American Numbering Machine Company, which had moved in after construction was completed in 1912. This company made hand stamps like those used in libraries to stamp the current date in books, as well as others for printing serial numbers or batch numbers, etc. It is not clear what relationship the two companies was. The American Numbering Machine Company stayed at this address until at least 1973, but this building is now a Christian centre or church.

Somewhere around 1930-1935 the Denominator Adding Machine Company moved to Woodbury, Connecticut, (though a Brooklyn address was kept on for many years) and shortened its name to The Denominator Company. The counters were redesigned to be modular so that it was easier to make them of any size. Some included a totalizer counter which could lock when the total reaches a multiple of 100. Note that Woodbury is only 20 miles from Bristol, where the Veeder-Root company were based. Veeder-Root made counters and measuring devices. It seems there was some kind of partnership between the two companies, because some of the new modular Denominator counters were marked with a patent number which was assigned to Veeder-Root.

In around 1950 the counters were redesigned again to have a plastic case. Each counter either had a large coloured button, or the whole top part of the case would act as the button for the counter. The company still exists today, run by the descendants of Frank Morse, and still produces similar types of counters.


1915-01-08 The Brooklyn Daily Times (New York)
1915-09 Office Appliances 1
1915-11-25 The Iron Age
1915-12 Office Appliances
1922 Brooklyn and Queens, New York, copartnership and corporation directory
1924 The American Digest Of Business Machines
1925 Ernst Martin
1930 Organisations-Lexikon - Denominator
1937-09-17 The Brooklyn Citizen (New York)
1950-01-26 The Brooklyn Daily Eagle (New York)
1950-07 Traffic Engineering
1952 Catalog of Copyright Entries Commercial Prints and Labels
1953 Catalog of Copyright Entries Commercial Prints and Labels
1953-03-08 The Brooklyn Daily Eagle (New York)
1954-05 Sigma Phi Epsilon Journal
1955-05-14 National Post (Totonto Canada)
1956-05-12 National Post (Toronto Canada)
1957-05-18 National Post (Toronto Canada)
1959 Official gazette of the United States Patent Office
1968-09-03 Oakland Tribune (California)


I found very few ads from before 1950, so I have included two for the American Numbering Machine Company with which the Denominator Adding Machine Company shared their factory.

1915-08-07 Boston Evening Transcript (Massachusetts)
1915-09 Office Appliances 2
1917-03 The Inland printer
1920-04 The Inland printer
1939-09 The American City
1950-06 Traffic Engineering
1950-07 American Fruit Grower
1950-09 Traffic Engineering
1950-12 American Business
1951-03 The Office
1951-03 Traffic Engineering
1951-05 The Office
1951-05 Traffic Engineering
1951-09 Public Safety
1951-10 American Business
1952-01 The Office
1952-02 American Business
1952-03 The American City
1952-03 The Office
1952-05 The American City
1952-07 The American City
1952-07 The Office
1952-08 American Business
1952-08 Bankers' Monthly
1953-01 The Office
1953-03 Best's Review
1953-03 The Office
1953-05 The Office
1953-10 The Office
1953-11 The Office
1954-05 The Office
1954-07 The Office
1955-02 Business Management
1955-04 Business Management
1955-05 The Office
1955-06 Law and Order
1955-07 Administrative Management
1955-07 The Office
1955-08 Business Management
1955-09 Administrative Management
1955-09 Traffic Engineering
1955-10 Flow
1955-10 The Office
1955-11 The Office
1956-01 The Office
1956-02 Administrative Management
1956-02 The Office
1956-03 The Office
1956-04 Administrative Management
1956-06 Administrative Management
1956-10 Administrative Management
1957-01 The Office
1957-05 The Office
1957-08 The Office
1957-12 The Office
1958-02 Business Management
1958-04 Business Management
1958-05 The Office
1958-08 Business Management
1958-08 The Office
1959-04 The Office
1959-07 The Office
1959-08 Business Management
1959-10 Business Management
1960-03 The Office
1960-07 The Office
1960-10 The Office
1961-03 The Office
1962-05 The Office
1967-07 Burroughs Clearing House


PatentFiling datePublish dateNameDescription
US 1,444,58609-03-192106-02-1923William A. Cook and Joseph LevineDenominating Apparatus.
US 2,175,62119-08-193610-10-1939Anton van VeenTotalizer for counting machines.
US 2,212,87002-09-193727-08-1940Edward Wild; Veeder-Root Inc.Counting mechanism
US 2,572,78402-03-194923-10-1951Anton van VeenHand-operated Counter or tally.
US 2,762,56708-10-195111-09-1956Anton van VeenTotalizer counter having means for stopping operation on reaching a predetermined number.


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