Operating a Comptometer

Plus & Sumlock Mechanical Calculators
Plus 506/D

PLUS 506

PLUS model 506/D/815.357.

Simple "Comptometer" type adder.

185 mm x 180 mm x 127 mm. (7.25" x 7" x 5").

This style casing was introduced in 1958.

One of the more minimalist calculators made. Has 6 decades of keys, with only 1 to 5. To enter a number between 6 and 9 two keys have to be pressed in that column. The knob on the right is for clearing the total.

Made in England by Bell Punch Co. Ltd. and distributed by Sumlock Compometer Ltd.

Capable really only of adding lists of numbers to 9,999,999, but capable of doing this quickly and accurately (and cheaply !).

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Introduction
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
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Summary
The Technology Explained
Operating a Comptometer
Old Sterling Currency, £sd
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Plus & Sumlock Mechanical Calculators

Petter S
Plus 506
Plus 509
PLUS 509 Time Calculator
PLUS 509 Weight Calculator
Plus 512
Sumlock 912
Sumlock 912 with Certopost
Sumlock 912 Weight Calculator
Sumlomatic
Sumlock Comptometer 993m
Sumlock Comptometer 993s

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