Duo Comptometer


This full-keyboard non-printing adding machine has a black metal case with six columns of black and white, octagonal keys, colored according to the place value of the digits entered. Complementary digits are indicated on the keys. Keys representing even digits are flat, those for odd digits are indented. In back of the keyboard is a movable carriage that contains a counter register and a result register above it. Numbers in the counter register can have up to seven digits. Those in the result register 13 digits.

To the left of the number keys are two white keys, one for the key drive and one for the crank drive. To the right of the number keys is a white key that, when pushed, releases the keys. On the right side of the machine is a crank that may be rotated to enter numbers into the register when the “crank drive” key is pushed down. The machine is designed to combine key-driven addition and crank-driven multiplication. It is the first model of a “Duo” Comptometer, and comes from the collection of models at Felt & Tarrant Manufacturing Company. There is no provision for subtraction.

A patent for the invention was filed July 31, 1923 and granted just over nine years later on August 2, 1932. It is patent 1,869,872. A metal tag stored with the object is marked: 134.

Reference: Felt & Tarrant, Accession Journal 1991.3107.06.

Date Made: 1922

Maker: Felt & Tarrant Manufacturing Company

Location: Currently not on view

Place Made: United States: Illinois, Chicago

Subject: Mathematics


See more items in: Medicine and Science: Mathematics, Adding Machines, Science & Mathematics


Exhibition Location:

Credit Line: Gift of Victor Comptometer Corporation

Data Source: National Museum of American History

Id Number: MA.323651Catalog Number: 323651Accession Number: 250163

Object Name: adding machine

Physical Description: wood (overall material)steel (overall material)plastic (overall material)Measurements: overall: 16.4 cm x 35.6 cm x 34.5 cm; 6 15/32 in x 14 1/32 in x 13 19/32 in

Guid: http://n2t.net/ark:/65665/ng49ca746a5-10e9-704b-e053-15f76fa0b4fa

Record Id: nmah_690475

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