Comptometer Model C

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This key-driven non-printing adding machine has ten columns of black and white color-coded keys. Complementary digits are indicated and the keys are alternately concave (odd digits) and flat (even digits). The key stems become progressively longer as the digits are larger. There are subtraction levers and decimal markers (unnumbered) in front of the keys. In front of these is a row of 11 windows in the brown steel case that reveals the result on numeral wheels below.
The machine has serial number 36372, which is indicated on the front to the left of the keys. It is marked on a metal tag screwed to the top of the machine: TRADE COMPTOMETER MARK (/) PAT’D [. . .] JUL.14.03 (/) Felt & Tarrant Mfg. Co. (/) Chicago. The date listed is the last of several patent dates on this tag.
The model C Comptometer went on the market in 1909. This example was first used at a commercial bank in Westfield, Massachusetts. In about 1950, it was given to Harry Rapp, on of the bank directors, as a relic. He in turn gave it to Judith Lowell in about 1965. She put it to use in the office of her husband, the physician Milton Lowell of Potsdam, New York, even though the Lowells already had a more recent printing machine. Not long after Dr. Lowell retired in 1984, the couple gave the Comptometer to the Smithsonian.
U.S. Patent #960528
J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1924, p. 548.
Accession File.
Currently not on view
date made
Felt & Tarrant Manufacturing Company
place made
United States: Illinois, Chicago
Physical Description
steel (overall material)
plastic (overall material)
overall: 14.5 cm x 27.5 cm x 37 cm; 5 23/32 in x 10 13/16 in x 14 9/16 in
ID Number
catalog number
maker number
accession number
Credit Line
Gift of Milton and Judith Lowell
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Adding Machines
Data Source
National Museum of American History


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