Webb Adder

This two-wheeled steel stylus-operated non-printing adding machine has a large wheel with the numbers 00 to 99 stamped around the edge. A smaller wheel has numbers 0 to 49 stamped around its edge. A ring of holes is inside each set of numbers. A metal plate covers the outer edges of the two wheels, revealing sums in a small window between them. The numbers 0 to 99 also are stamped around the window for the larger wheel. Numbers are added by rotation of the wheels, up to sums of 4999. The carry mechanism is that patented by L. C. Smith. The frame is smooth around the edge, and patterned on the back. The stylus is missing and there are no maker’s marks.
This instrument is from the collection of Felt & Tarrant Manufacturing Company.
Lester C. Smith, “Adding-Machine,” U.S. Patent 414335, November 5, 1889.
P. Kidwell, “The Webb Adder,” Rittenhouse, 1 (1986), pp. 12-18.
E. Martin, The Calculating Machines (Die Rechenmaschinen), trans. P. A. Kidwell and M. R. Williams, Cambridge: MIT Press, 1992, p. 63.
Currently not on view
Object Name
adding machine
date made
ca 1890
Webb, Charles H.
Physical Description
steel (overall material)
overall: .5 cm x 16.1 cm x 11.1 cm; 3/16 in x 6 11/32 in x 4 3/8 in
place made
United States: New York, New York
place patented
United States: New York, New York
ID Number
accession number
catalog number
Science & Mathematics
Adding Machines
See more items in
Medicine and Science: Mathematics
Adding Machines
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Victor Comptometer Corporation

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