Silver plated and gold plated Sovereigns, with leather pouches and fitted wooden case.
The above photographs of the silver plated and gold plated Sovereigns courtesy of Anoop Sahal.
Display is 8 digits, red LED.
4 function, %, memory, square root, square.
2.5v (2x button cells).
Main integrated circuit - Mostek MK50321N.
36 x 141 x 12 mm (1.4 x 5.6 x 0.5 ins).
Made in England.
Is very small and slim.
The Sovereign was one of the last Sinclair models, from 1976, and was an attempt to move up market. Although looking very classy, it still retained the tiny power hungry LED (Light Emitting Diode) display.
Cheap small calculators with large LCD (Liquid Crystal Display) readouts were becoming very common, and ther batteries lasted for months or years.
Sinclair shortly dropped its calculator range and concentrated on personal computers.
The Sovereign is unusual in that the casing is made from pressed steel. This allowed a variety of paint and plating options, including black painted, bright chrome plated, silver plated, and gold plated (see above photographs). It is also reported that a small number of solid gold ones were made. In 1976 the chrome plated version cost £30 Sterling (US$60) and the gold plated version cost twice as much.
Below is a limited edition silver plated version, inscribed to commemorate the Silver Jubilee of Queen Elizabeth II in 1977.
Sinclair was renowned for squeezing electronics into the smallest space possible. This is illustrated below in the Sovereign where the casing has been removed.
The front and rear of the casing are made of pressed steel pushed onto a central plastic frame. From left to right above are the plastic frame with the rear of the casing in place underneath, the circuit board, and the casing front. The front side of the circuit board has the LED display at the top, with the display driver integrated circuit below, and the keyboard.
The rear of the circuit board carries the Mostek MK50321N calculator IC and two transistors.
Grateful thanks go to Neelesh Sonawane for donating this example to the Vintage Calculators Web Museum for spares, since the case was in poor condition. This gave the opportunity to open the machine and examine the circuitry.
© Text & photographs copyright Nigel Tout 2000-2015 except where noted otherwise.