Historical information

1946 One of the first Contex calculators, the Half-Keyboard Adder used Leibniz step cylinders to perform simple addition. The predominant use of this Contex would have been adding sterling currency. Starting from the right, the levers were used for half and quarter pence, the next row would be pence, followed by shilling up to 19, and pounds. On the far left there is a zeroing lever for the entire mechanism; Ref: Online: 'physicsmuseum.uq.edu.au'


Used by the office staff at the SECV construction of the Kiewa Hydro Electric Scheme.

Physical description

Bakelite small typing machine consisting of numbers with a screen above.

Inscriptions & markings

'Context' embossed centre front
'Lubrication' with instructions and with Patents on bottom
'Chartres Business Service' at back
'Numbers 1 - 5' at front on knobs