Texas Instruments SR-51A Handheld Electronic Calculator

This handheld electronic scientific calculator has a black plastic case with an array of forty small rectangular plastic keys. The white digit keys, a decimal point key, and a change sign key have only one meaning. The orange total key also has only one meaning. Pushing the gold “2nd” key changes the function of the other keys from what is shown on the key to the “dual function” indicated above it on the keyboard. The device calculated values of a wide range of arithmetic, statistical, logarithmic, trigonometric, hyperbolic trigonometric, and inverse trigonometric functions using the gold and brown keys. It also has limited memory.
Text above the keys reads: TEXAS INSTRUMENTS SR-51A. Behind the keyboard is a switch that may be set at R (radians) or D (degrees). Next to it is an on/off switch. Behind the keyboard is an LED display that shows ten-digit positive and negative numbers and two-digit positive and negative exponents.
The calculator has a jack for a recharger/adapter along the back edge. A sticker on the back gives codes entered to convert from common measures to metric measures and vice versa. It reads in part: TEXAS INSTRUMENTS (/) SR-51A. It also gives the serial number SR-51A 125990. Text at the bottom of the sticker reads: Assembled in USA. Text below the sticker reads: 4575DTA. Above the sticker is a compartment for a battery pack. An owner’s mark along the side of the calculator reads: Joanna Spain 550-25-3136. The same mark is on the inside of the back of the calculator.
Unscrewing four screws on the back reveals the workings of the calculator. It has six chips, two relatively large. One of the large ones is marked: TMC0523NL (/) AΔ7529-5. This is a TMC0523 chip, manufactured in mid-1975. The other is marked: TMC0501NL (/) DΔ7531-6. This is a TMC0501 chip, manufactured the same year.
The calculator comes in a black plastic, zippered case with belt loop.
Compare 1986.0988.357 (the SR-51) and 1986.0988.358 (the SR-51 II).
The 1977 yearbook of the University of Arizona lists a student named Joanna Spain as an underclassman. See p. 125.
[Advertisement], Chicago Tribune, July 10, 1975, p. 9. New Texas Instruments SR-51A on sale for $149.
[Advertisement], Washington Post, August 21, 1975, p. A4. Give sale price of $134.95, regular price $149.95.
[Advertisement], Los Angeles Times, January 3, 1976, p. C5. Give price of $103.95.
[Advertisement], Los Angeles Times, September 4, 1976, p. C4. Give price of $62.95, regularly $79.95.
Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 154. They give a 1975 price for the SR-51A calculator of $109.50.
Currently not on view
Object Name
electronic calculator
date made
Texas Instruments
Physical Description
plastic (case; keys; carrying case material)
metal (circuitry; zipper material)
paper (sticker material)
overall: 1 1/4 in x 3 1/8 in x 5 3/4 in; 3.175 cm x 7.9375 cm x 14.605 cm
ID Number
catalog number
accession number
See more items in
Medicine and Science: Computers
Handheld Electronic Calculators
Computers & Business Machines
Data Source
National Museum of American History, Kenneth E. Behring Center


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