Texas Instruments TI-2550 III Handheld Electronic Calculator

In 1972 Texas Instruments began selling electronic calculators under its own name. The first of these was the Datamath or TI-2500. Over the next few years, TI sold modifications of the TI-2500 that had different forms of battery (such as the TI-2500B, the TI-2500II, the TI-2510, and the TI-2550III), a different color case (the TI-2510 and the TI-2550III), a key for taking percentages (the TI-2550, the TI-2550II, and the TI-2550III), and keys for additional functions (the TI-2550, the TI-2550II and the TI-2550III). This is an example of the TI-2550III.
The calculator has an array of thirty-five rectangular plastic keys. These include ten digit keys, four arithmetic function keys, a clear key, a clear entry key, a decimal point key, and a total key. Also included are a change sign key, a percentage key, four memory keys, an inverse key, a square key, a square root key, and a reverse entry (RV) key. The RV key replaced an entry in the display with the immediately preceding entry.
The on/off switch is above the keyboard on the right. A mark above it reads: TEXAS INSTRUMENTS TI-2550III. Behind this is an eight-digit blue vacuum fluorescent display.
There is a jack for a power adapter along the back edge (according to instructions for the calculator found online, this would have part number AC9310A). The back has a battery compartment that would hold a rechargeable battery pack (according to instructions for the calculator, this would have model number BP-3).
A sticker on the back of the calculator reads in part: US PAT 3819921 OTHER PATENTS PENDING (/) TEXAS INSTRUMENTS (/) TI-2550-III (/) electronic Calculator (/) Serial No. (/) 2550-III 075877. It also reads in part: ASSEMBLED IN USA. A mark below the label reads: 4576LTA.
Unscrewing four screws from the back of the calculator reveals the circuit board. The largest chip is marked: TMS1043NL (/) KBSΔ7642.
The calculator has a black plastic zippered case.
[Advertisement], Boston Globe, November 25, 1976, p. 92. Selling for $29.95.
[Advertisement], Los Angeles Times, January 29, 1977, p. C5. Advertised as selling for $28.95.
Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 158. They give a 1976 price of $34.95.
Online Datamath Museum.
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 in x 5 3/4 in; 3.175 cm x 7.62 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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