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Time Calculators

Plus Time Comptometer

Plus Time "Comptometer"

This is a direct action keyboard calculator of the "comptometer" type. It has an abbreviated keyboard (keys up to 5) and is designed for calculations in hours and minutes (model Plus 509/T/828599, made by Bell Punch Co. Ltd. in Britain, distributed by Sumlock Ltd., both owned by Control Systems Ltd.).

235 x 182 x 120 mm (9.25" x 7.2" x 4.75").

Manufactured about the 1950's-1960's.

The keyboard of this machine has keys with, from the left, 7 columns of Hours keys, and 2 columns of Minutes keys.
Although from the outside the machine is similar to a normal decimal machine, inside it is geared to carry over when the second column from the right reaches 6, i.e. 60 minutes carries over to 1 hour.

To enter a number above 5 the operator has to press two keys in that column, one after the other, which add up to the number required.

The machine in the photographs above and below displays the total of 123 Hours and 55 minutes. By adding 5 minutes (i.e. pressing the 5 key in the right hand column) would produce the result 124 hours 00 mins.


This machine would have been very useful in the wages department of a company, totalling the hours worked.

Time has not been metricated, so there is still the need to calculate in hours and minutes. The Casio AL-8 was one of the first electronic hand-held calculators to be able to calculate hours, minutes, and seconds.
Electronic calculators are available for the television industry which can calculate in hours, minutes, seconds, and frames for various broadcast standards.


There are instructions for the basic use of Comptometer-type machines in the article "Operating a Comptometer" on this site.


For information about the Bell Punch company and its calculators see the article on this site "Anita: the world's first electronic desktop calculator - A brief history of the complex Bell Punch company and its calculators".

For a detailed history of the development of the Bell Punch and Anita calculators go to the associated site "Bell Punch Company and the Anita Calculators".

Click here for more information about Comptometers.

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2022  except where noted otherwise.