In 1972, Hewlett Packard launched the HP-35, the world's first handheld scientific calculator. Despite market research suggesting that it was too expensive for there to be any real demand, production went ahead. It cost £165, around £2,800 in today's money but despite the price, over 300,000 were sold in the three and a half years for which it was produced.

From 1971, Texas Instruments had been making available the building block for a simple calculator on a single chip and the TMS0803 chipset appeared in a number of Sinclair calculators. Clive Sinclair wanted to design a calculator to compete with the HP-35 using this series of chips. Despite scepticism about the feasibility of the project from Texas Instruments engineers, Nigel Searle was able to design algorithms that sacrificed some speed and accuracy in order to implement scientific functions on the TMS0805 variation.

The Sinclair Scientific first appeared in a case derived from that of the Sinclair Cambridge, but it was not part of the same range. The initial retail price was £49.95 in the UK (equivalent to £676 in 2026), fully assembled. By July 1976, however, it was possible to purchase one for £7 (equivalent to £65 in 2026).

This calculator being sold here was given to me by may Farther when I finished my apprenticeship in electronic engineering. Boy, could I have done with it at college. It's one of the earliest sold and is highly collectable. Fully working but with some age-related discolouring. Supplied without batteries. (4 x AAA required).