Plus & Sumlock Mechanical Calculators
Plus 506/F
PLUS model 506/F.
Simple "Comptometer" type adder for old £sd Sterling currency, with farthings.
170 mm x 190 mm x 118 mm. (6.7" x 7.5" x 4.6").
One of the more minimalist calculators made. Has 2 decades of £ keys, shillings, pence, and farthings (quarters of a penny) keys, with each decade numbered from 1 to 5. To enter a number between 6 and 9 (or 11 in the case of the
pence column) two keys have to be pressed in succession in that column. The knob on the right is for clearing the total.
The machine illustrated shows the total £12 17s 11 3/4d.
Made in England by Bell Punch Co. Ltd. and distributed by Sumlock Compometer Ltd.
The machine illustrated has serial number 506/F/45.74, and has the older, rounded style casing. The farthing ceased to be legal currency in Britain in 1961, when this model would have become obsolete.
