Plus & Sumlock Mechanical Calculators
London Computator Corporation 509/S
London Computator Corporation model L.C/509/S.
Simple "Comptometer" type adder for old Sterling £sd currency.
275 x 188 x 118 mm (10.8" x 7.4" x 4.6").
Has 6 decades of £ keys, with shillings and pence keys in columns on the right, all abbreviated to 1 to 5. To enter a number between 6 and 9 two keys have to be pressed in succession in that column to give the required number.
The lever on the right is for clearing the total.
The machine in the photograph above shows the total £123,456 17s 6d.
It is labelled "Manufactured by London Computator Corporation Ltd., 39 St. James's St., London SW1.
Sole distributors ADDO CO. (Britain) Ltd."
The machine illustrated has serial number L.C/509/S/1445.
The London Computator Corporation, Limited, was formed by Bell Punch to deal with the sales side of the Plus and Sumlock machines. However, it is odd that this machine is not labelled "Plus", and that it is distributed by a
completely separate company, Addo.
London Computator Corporation Ltd. was renamed Sumlock Limited in 1950.
The machine with its cover removed.
There are excellent photographs and descriptions of the Plus Adder mechanism at John Wolff's Web Museum site. These are accessed from the Comptometers and Key-Driven Calculators section on that site.
