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(since April 22, 1997)

Last Update: August 18, 2021 -- THE CURTA REFERENCE

Texas Instruments Calculators

(1972-79) - How rare are they?

by Larry Gilbert

Texas Instruments" and "rare" sounds like a contradiction. Anyone who searches for early electronic calculators quickly senses the extent to which TI dominated the market in the 1970s. A count through my own collection revealed over 40 different models and there are many I don't have! It would be easy to conclude that all TI calculators are commonly found and not much of a challenge to the avid collector.

However, this is not the case. There are many rare models and a few less-common variations of well-known models. TI had a tendency to replace their calculators quickly with improved or lower-priced versions, particularly during the price wars of the mid-70s. They also had such extensive product lines at times that their own products must have competed against each other.

For this article, I divided TI calculators into four categories based on degree of rarity. The judgments are based on my experience searching through flea markets, garage sales, thrift shops, and collector lists (and encountering thousands of calculators in the process), on numerous conversations I have had with other collectors, and on some library research. The year of introduction is noted in parentheses following the model number.

Very common:



Difficult or Very Difficult:

TI made calculators for sale under other names, including Radio Shack. These are more difficult to locate than the TI versions. Some examples are (1) the Longines Symphonette 2500, a clone of the TI 2500 Datamath (2nd version), but in a green color, (2) the Exactra line (models 19, 20, 21, 22, and 23), reminiscent of the more colorful 1200 models, but sold as early as 1973, and (3) many Montgomery Ward models (identified by the "TXI-" prefix to the model number). The Montgomery Ward calculators are especially fascinating as they are not obvious clones yet can be identified as related to specific TI models.

Some models are difficult to find in good condition. The SR-10 and 11 are notorious; the silver trim is almost always worn on these models. An SR-10 in near mint condition would definitely qualify as "Difficult". The SR-50, 51, and 52 suffered from paint wear around the switches and later TI models often have loose nameplates and missing battery covers. Other models, such as the 2500 and 2550, are usually in quite nice condition. Most models are rarely found with the original box and paperwork; out of dozens of TI 30s that I have seen, only 1 or 2 have been new-in-box. Interestingly, some of the earlier models, such as the SR-10 and SR-50, appear to be easier to find with the box, although the boxes tend to show wear easily.

Since my article first was printed, I have discovered/been informed of additional models, which all appear to be somewhat rare. These include:

Finally, TI calculators often have a data code stamped on the back. It appears to consist of a two-digit week and two-digit year, such as "4376", for the 43rd week of 1976. TI chargers, too, have date codes, expressed as month and year, such as "7 72".

Rick Furr (
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