Sinclair Executive.

Launched in the summer of 1972, the Executive was the first Sinclair calculator, and by a clever circuit design was the world's first calculator to be powered by button cells.  This allowed it to be incredibly thin for the time at 9mm, 0.4".

This is a featured calculator.

Sinclair Cambridge.

The first Sinclair Cambridge model was introduced in summer 1973.  There followed a range of a dozen or so models and variations.

This is featured on the associated British Vintage calculator site.

Sinclair Scientific.

By a clever choice of algorithms and elctronics Sinclair was able to produce a very small, low-cost, Scientific calculator, using RPN (Reverse Polish Notation).

This is a featured calculator.

Sinclair Oxford 200.

There are several models in the Oxford range, and some were made in an LED version and also, probably later, in a VFD (Vacuum Fluorescent Display) version.

These are featured on the associated British Vintage calculator site.

Sinclair Sovereign.

By 1976, with the market flooded by many cheap models, Sinclair was struggling to make a profit from its calculators.  The Sovereign was one of the last Sinclair models, and was a move by the company to a very stylish, tiny, high-quality calculator that it could sell for a higher price.

This is featured on the associated British Vintage calculator site.

Sinclair Wrist Calculator.

This was one of the last calculators designed under Clive Sinclair, in 1977.

This is a featured calculator.