Operating a Comptometer

Plus & Sumlock Mechanical Calculators
PLUS 509/Y Imperial-Weight Calculator

PLUS 509 Imperial-Weight Calculator

Plus model 509/Y/876.514 Imperial-Weight abbreviated "Comptometer".

This is a direct action keyboard calculator of the "comptometer" type with an abbreviated keyboard for calculations in Imperial weight units.

241 x 182 x 177 mm (9.5" x 7.2" x 7.0").

This style of casing was introduced in 1958.
Made by Bell Punch Co. Ltd. in England, distributed in U.K. by Sumlock Comptometer Ltd.

This machine has an abbreviated keyboard - it only has keys 1 to 5 in the standard decades columns, so to enter a number greater than 5 you have to press one key followed by another which add up to the number required.

The machine in the photographs displays the total of 1 Ton, 19 Hundred-weights, 3 Quarters, and 27 Pounds.


Close up of the keyboard of this imperial-
weight calculator.


With the cover removed. The standard, decimal columns use plastic gear wheels, while the non-standard columns use metal gears. It was probably not economical to make the moulds for these non-standard items


With the cover removed, from the rear.

Fortunately, Britain changed to the metric system during the 1970s and 1980s and this complicated system of units is now virtually obsolete. It does not appear to have been used in modern times in the U.S.A. where weights are customarily given in Pounds (lbs) only.

No electronic calculators are known to have been sold which use this weight system, though a Sumlock-Anita engineer says that he was involved in the modification of some Anita electronic calculators to this system for Britain's National Coal Board in the late 1960s.

Origins of Bell Punch Co.
All Change at Bell Punch
Development of Anita 1
Development of Anita 2
Anita is Launched
At work with Anita
National Calculating Service
Anita Developed Further
Anita at its Zenith
The Rockwell Connection
Demise of Anita & Bell Punch
Mechanical Calculators
Early Anita Desktop Calculators
Transitors & Integrated Circuits
Anita LSI Desk Calculators
Anita Hand-held Calculators
Rockwell-Anita Calculators
Calculators made by others
The Technology Explained
Operating a Comptometer
Old Sterling Currency, £sd
Update Information

Plus & Sumlock Mechanical Calculators

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Sumlock Comptometer 993m
Sumlock Comptometer 993s

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Text & photographs copyright © 2002, 2003 Nigel Tout, except where noted otherwise.