APF Mark 31 Handheld Electronic Calculator

This handheld electronic calculator has an array of ten brown plastic keys for digits and a decimal point. Above these are inversion, squaring, and square root keys. To the immediate left is an x/y exchange key, a percentage key, keys for the four arithmetic operations, and an equals/constant key. Left of these is a clear entry/clear key and a set of five memory keys. A mark above the switch reads: aPF MARK 31.
Behind the keyboard is an eight-digit display.
The back of the calculator has a compartment for a battery but no battery or compartment cover. A silver-colored sticker pasted to the back reads: aPF mark 31 (/) SLIDE RULE CALCULATOR. It gives operating instructions. The bottom of this label reads: MARK 31 (/) Model No. It also reads: MT-019962 (/) Serial No. Further text reads: APF ELECTRONICS INC. (/) NEW YORK, N.Y. 10022 (/) MADE IN JAPAN. A mark in the bottom left corner reads: 7545. The top edge of the calculator has a hole for an adapter but no adapter.
An August 1976 advertisement in the Los Angeles Times lists the APF Mark 31 as on sale for $19.99. An October 1976 advertisement in The Chicago Tribune gives a regular price of $14.95 and a sale price of $13.99. An ad in the Los Angeles Times the same time gives the same prices.
Compare 1986.0988.083 (the Montgomery Ward P203).
Los Angeles Times, August 25, 1976, p. 11.
Los Angeles Times, October 17, 1976, p. M20.
Chicago Tribune, October 17, 1976, p. 40.
Currently not on view
Object Name
electronic calculator
date made
ca 1976
APF Electronics
Physical Description
plastic (overall material)
paper (sticker material)
rubber (feet material)
metal (circuits material)
overall: 1 in x 3 in x 5 3/4 in; 2.54 cm x 7.62 cm x 14.605 cm
place made
ID Number
catalog number
accession number
Handheld Electronic Calculators
Computers & Business Machines
See more items in
Medicine and Science: Computers
Handheld Electronic Calculators
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of John B. Priser
Additional Media

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