Plus & Sumlock Mechanical Calculators
Sumlock 912/F Sterling Currency Calculator with Farthings keys.

Sumlock 912/F

SUMLOCK model 912/F Sterling currency "Comptometer" with Farthings keys.

This is a full-keyboard direct action calculator of the "comptometer" type for Sterling currency calculations. It is similar to the 912/S machine except that it gains three farthing (1/4 penny) keys on the right by losing a column of pound keys on the left.

330 mm x 315 mm x 135 mm (13" x 12.5" x 5.5"), 7 Kg (15.5 lbs).

Manufactured about the 1950's to early 1960's .
Made by Bell Punch Co. Ltd. in Britain, distributed by Sumlock Ltd.

This machine has a full keyboard except for the Pence column where there are only 9 keys (1-9) instead of 11 in a fully keyed model, although the accumulator for this column will display up to 11. The tens of shillings column only has the one key necessary.

To enter 11 in this column the operator has to press in turn the (9) key and the (2) key.

This plays off ease of use compared with lower manufacturing cost in that more standard components can be used.

This machine was photographed at the computing museum at Bletchley Park, England, but items on display vary.

The farthing ceased being legal tender in Britain in the early 1960s.
See the Old Sterling Currency section for more information on the pre-decimalisation money system used in Britain and the British Commonwealth.

There is an operating manual for the Sumlock "Comptometer"-type machine in the Operating Manuals section of this site, with a summary on the Operating a Comptometer page.

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Text & photographs copyright © 2002 - 2023 Nigel Tout, except where noted otherwise.