Carroll Adding Machine

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This is the U.S. Patent Office model for a nine-key non-printing adding machine. The small machine has a wooden case with nine metal keys with wooden key covers, arranged in two rows. There are three wooden numeral wheels visible through a window at the back top. The machine apparently is designed to add single digits up to 999. No numbers are visible on the key tops. The keys in each row presently appear to operate [no effect] 4 6 8 (/) [no effect] 2 3 5 7. The patent drawing indicates that the keys are arranged 2 4 6 8 (/) 4 5 5 7 9. The effect of the keys is determined by adjusting screws on the underside of the machine. The four registering wheels to the left have on their left side a ring of ten equidistant pins that are used in carrying. There is a lever at the top of the machine that can be adjusted to release the number wheels so that they can be turned back to zero using a button on the left. The device was patented by David Carroll of Spring Creek, Pennsylvania.
David Carroll, “Improvement in Adding Machines,” U.S. Patent #176,833, May 2, 1876.
E. Martin, The Calculating Machines (Die Rechenmaschinen), trans. P. A. Kidwell and M. R. Williams, Cambridge: MIT Press, 1992, p. 75.
Currently not on view
date made
Carroll, David
Carroll, David
place made
United States: Pennsylvania, Spring Creek
place patented
United States: Pennsylvania, Spring Creek
Physical Description
wood (overall material)
metal (overall material)
overall: 10.8 cm x 12 cm x 18 cm; 4 1/4 in x 4 23/32 in x 7 3/32 in
ID Number
accession number
catalog number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Adding Machines
Data Source
National Museum of American History


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