Sinclair Wrist Calculator
Sinclair Wrist Calculator
Display is 8 digits, red LED.
4-functions, %, memory, square root.
8.1v (6x mercury cells).
Integrated circuit - Mostek MK50321N, here date coded mid-1976.
47 x 45 x 18 mm (1.9 x 1.75 x 0.7 ins).
Made in England.
Launched in February 1977.
Was available only as a self-assembly kit, by mail order from Science of Cambridge, previously Sinclair Instrument Ltd., which had been founded by Clive Sinclair and to which he moved from Sinclair Radionics. (There is a brief history of Clive Sinclair, his companies, his calculators, and other products in the article Clive Sinclair and the pocket calculator in the Collecting Calculators section of this site.)
There appear to be two versions of this calculator, see photograph below.
Total price was only £11 Sterling (about US$20).
Although combined watch-calculators became very popular, starting with LED display models such as the Pulsar and Compuchron, only two models of pure wrist calculator are known, the Sinclair and the Quik Check.
Clive Sinclair was always interested in making tiny versions of common electronic items. Here, into the smallest practical volume he managed to squeeze the LED display and chip used in other Sinclair calculators (the Sinclair Cambridge Memory and Cambridge Universal), which were then becoming obsolescent.
