Wales Model 20 Adding Machine

This full keyboard printing manually operated adding machine has a metal frame painted black with a glass panel in front of the number dials. Nine columns of black and white color-coded plastic keys arise from a the metal keyboard that is painted green. Total and subtotal keys are to the left of the keyboard. Red plastic repeat and correction keys are above the number keys, and a key stem and non-add key are behind the numeral dials. These nine dials are behind the keyboard, with divisions for U.S. currency indicated. The metal crank for operating the machine is on the right. At the back of the machine is the printing mechanism and a 13-inch (33 cm.) movable carriage. A bell is at the far left of the carriage. There is a two-color ribbon. The machine is extremely heavy.
The machine is marked on the front, and on the front of the carriage: WALES. It is marked above the keyboard: MANUFACTURED BY (/) THE ADDER MACHINE COMPANY (/) WILKES-BARRE, PA.,U.S.A. It is marked on the back with a list of 19 patent dates. The first of these is: PATENTED DEC. 1. 1903. The last is: JULY 5. 1913. It is marked on the carriage: 2065. The serial number, shown on the front of the machine at the bottom, is: 20-40243.
There is a metal stand painted black, with a wooden table on the right side. The stand is stored separately. Its dimensions are: 56 cm. w. x 57 cm. d. x 79 cm. h., with writing table down.
Compare to MA*323593.
J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1924, pp. 60-61, 544-545.
Currently not on view
Object Name
adding machine
date made
Adder Machine Company
Physical Description
plastic (overall material)
glass (overall material)
metal (overall material)
rubber (overall material)
wood (overall material)
overall: 29 cm x 46.1 cm x 60 cm; 11 13/32 in x 18 5/32 in x 23 5/8 in
place made
United States: Pennsylvania, Wilkes-Barre
ID Number
catalog number
accession 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 Arlene W. Kettle
Additional Media

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