Comptometer Model A

Comptometer Model A

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This key-driven, non-printing adding machine is an early example of a Comptometer with a metal case.
It has eight columns of plastickeys. The keys in the two rightmost columns, which represent cents, are white, the three middle columns are black, and the three lftmost columns are white. Such color coding was common in machines designed for financial calculations. Complementary numbers are indicated. The keys are alternately concave (for odd digits) and flat (for even digits). The keys are worn, and one is missing. The key stems are flat, and become progressively longer as the digits become larger. The subtraction levers are at the same level as the decimal markers.
The nine numeral wheels are white or turquoise around the rim, depending on the decimal place of the digit indicated. They are visible through windows in the glass. The zeroing handle is on the left. The Model A Comptometer was Felt & Tarrant’s first “duplex” machine, in that it would add in more than one column at a time, each column having the capacity to add, receive, and carry simultaneously. This was not true of the earlier wooden box models.
The first Model A Comptometer was produced in January 1904 and had serial number 15000. Over 6,200 machines were produced in the next two years. This machine has serial number 17536, which is marked in the center front. It has a metal tag screwed to the top that reads in part: TRADE COMPTOMETER MARK. There are ten patent dates on this tag.
This machine came to the Smithsonian in 1981 from the collection of Esther S. and James C. Henderson, who ran an office equipment business in Corvallis, Washington.
For a related adding machine section, see MA.323643.
Felt & Tarrant, "Accession Journal ,"1991.3107.06.
J. H. McCarthy, American Digest of Business Machines, 1924, Catalog Section, p. 71.
Currently not on view
Object Name
adding machine
date made
Felt & Tarrant Manufacturing Company
place made
United States: Illinois, Chicago
Physical Description
plastic (overall material)
steel (overall material)
glass (overall material)
german silver (overall material)
wood (overall material)
overall: 14.2 cm x 23.5 cm x 37 cm; 5 19/32 in x 9 1/4 in x 14 9/16 in
ID Number
maker number
catalog number
accession number
Credit Line
Gift of Esther H. and James C. Henderson
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Adding Machines
Data Source
National Museum of American History
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