Dial-A-Matic Adding Machine

Dial-A-Matic Adding Machine

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The front of this instrument is a six-wheeled stylus-operated plastic adding machine. Each wheel has a ring of ten holes. The holes are numbered from 0 to 9 counter-clockwise around the outside and from 0 to 9 clockwise around the inside. Outer digits are for addition, and inner ones are for subtraction. Square windows above the wheels show the result. A zeroing bar is on the right and a short aluminum stylus is on the left. The instrument is mounted on a piece of fiberboard. Behind it, mounted on a piece of wood on the fiberboard, are two rods, with five dials on each rod. Each dial has the digits from 0 to 9 around the outside. Each rod and its mounting slide along a track at the top of the instrument. These rods and dials were added by the donor, the inventor Waldemar Ayres (b. 1909).
The instrument is marked on the front: Dial-A-Matic ADDING MACHINE. It is also marked there: SP (/) STERLING. The letters “SP” are in a circle. The New Jersey firm of Sterling Plastics used the trademark of SP in a circle with a clear background from 1945, registered this as a trademark in 1953, and renewed the trademark in 1973. The company first used the term Dial-A-Matic in commerce in 1954, registered it as a trademark in 1955, and renewed the trademark in 1975. The device is based on a patent taken out by Otto Lehre of Springfield, New Jersey. Lehre applied for a patent April 30, 1954 and received it in 1957. The object came to the Museum in 1974. Hence it was created between 1955 and 1974. It seems likely that it dates from about 1960.
Otto Lehre, "Calculator," U. S. Patent 2,797,047, June 25, 1957.
Currently not on view
Object Name
adding machine
date made
ca 1960
Sterling Plastics
place made
United States: New Jersey
Physical Description
fiberboard (overall material)
plastic (overall material)
brass (overall material)
aluminum (overall material)
wood (overall material)
overall: 6.3 cm x 30.6 cm x 14 cm; 2 15/32 in x 12 1/16 in x 5 1/2 in
ID Number
accession number
catalog number
Credit Line
Gift of Waldemar A. Ayres
See more items in
Medicine and Science: Mathematics
Adding Machines
Science & Mathematics
Data Source
National Museum of American History
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