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, and the TI-2510), a different color case (the TI-2510), a key for taking percentages (the TI-2550 and the TI-2550II), and keys for additional functions (the TI-2550, the TI-2550II and the TI-2550III). This is an example of the TI-2550.
The handheld calculator has a white plastic case with a black plastic keyboard. It has an array of twenty-three plastic keys, all but two of them square (the 0 and total keys are rectangular). These include ten digit keys, a decimal point key, a total key, four arithmetic function keys, a percentage key, a clear entry key, and a clear key. In addition there are four memory keys. Text above the keys reads: TEXAS INSTRUMENTS. Text below the keys reads: TI-2550.
Behind the keyboard is an eight-digit LED display it. Behind it, on the top right, is an on/off switch. Left of it is a “decimal select” switch which may be set at F (floating), 2, or 4 decimal places for the answer. A jack for an adapter/charger is along the back edge.
The back of the calculator has a compartment for storing either three rechargeable nickel-cadmium batteries of four AA-sized non-rechargeable batteries. The lock is at the bottom of the compartment rather than at the top as on earlier calculators like the TI-2500B.
A sticker on the compartment cover reads in part: TI-2550 memory calculator (/) Made by Texas Instruments Incorporated, Dallas, Texas. It indicates that the built-in battery gives four to six hours of portable operation and acquires a full recharge in ten hours with an AC9130 adapter/charger. (If non-rechargeable batteries were used, an AC9120 adapter was required). Further text on the sticker gives operating instructions. It also reads: Serial Number 2550 421312.
Unscrewing three long screws on the back of the case reveals one of two circuit boards. The chips are not visible.
The calculator has a black plastic zippered case that also holds an instruction manual with title: Texas Instruments (/) electronic calculator (/) TI-2550. A date on the back of this manual indicates it was copyrighted in 1974.
Ball & Flamm give a 1974 price of $99.95 for the calculator.
References:
Guy Ball and Bruce Flamm, The Complete Collector’s Guide to Pocket Calculators, Tustin, CA: Wilson/Barnett, 1997, p. 157.
[Advertisement], Boston Globe, April 17, 1974, p. 6. Jordan Marsh announces that the new “full memory” TI-2550 is in stock, selling for “only 99.95.”
[Advertisement], Los Angeles Times, October 6, 1974, p. I19. Gives price as regularly $99.95, reduced to $69.95.
[Advertisement], Chicago Tribune, May 27, 1975, p. 14. Announces that price reduced to $49.95.
[Advertisement], Boston Globe, September 7, 1976, p. 26. Advertised as on sale for $29.95.
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