The Wrist Calculator was launched in February 1977 by Sinclair Instrument, a company established in parallel to Sinclair Radionics when the latter started to encounter financial difficulties.
[1][2] Despite the difficulty in assembling the kit due to the small size of the parts and their variability in specification, 10,000 were sold around the world.
20,000 were exported to the United States, but most went unsold and were returned to Sinclair.
[3] The design used 10 keys, with a three-position switch to select the correct function.
[4] It used normal algebraic logic, as opposed to the reverse Polish notation employed on some Sinclair calculators.