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.

References:

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.

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