Plus & Sumlock Mechanical Calculators
PLUS 509/D
Plus model 509/D
Simple "Comptometer" type adder.
This is a direct action keyboard calculator of the "comptometer" type. It has an abbreviated keyboard (keys up to 5) and is designed for decimal calculations.
235 x 182 x 120 mm (9.25" x 7.2" x 4.75").
The machine illustrated has serial number 509/D/892604.
Made in or after 1966, when Sumlock Anita Electronics was formed to manufacture the electronic and mechancal calculators.
The label showing that this is a later machine, made when the manufacturing company was known as Sumlock Anita Electronics Ltd.
