Electromechanical calculating machines from the 1960's
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Rotary calculators
Badenia VA-17
Badenia VARE-17
Bohn Contex 55
Cellatron R44SM
Diehl DSR-18
Diehl VSR-18
Facit CA1-13
Friden SBT
Friden SVE
Friden SRW
Friden SRQ
Friden RSR
Hamann 505
Madas 20 BTG
Marchant ABL
Marchant SKA DeciMagic
Marchant Tenkeymatic
Monroe IQ-213
Olympia RA-16

Soemtron 214

Printing calculators



Other calculating devices

References and links



Bohn Contex 55        
  A/S Brdr. Carlsen
Birkerød, Denmark
  oscillating rack
Years produced
Price when new
  $349 in 1969, $190 in 1971
Size (W x D x H)
  lb. oz. (kg)
  semi-automatic multiplication
  click on photo to enlarge    

This compact Danish machine provided a low-cost alternative to the large and expensive full-keyboard rotary machines. Sigvard Bernadotte, a member of the royal family of Sweden, was responsible for the industrial design of this machine and the entire Contex line.

Unlike most machines in the collection, this machine is not fully automatic. It does not have a control register to keep track of the multiplier. Instead, the product is calculated for each digit of the multiplier individually as the digits are entered. The digits have to be entered in reverse order, since the machine has no way of knowing how many digits are yet to come.

It is also not a rotary calculator, since it employs an oscillating rack mechanism. This mechanism, more commonly found on adding machines, is slower than a rotary mechanism because half of the back-and-forth motion is wasted. Although it was designed to be an inexpensive machine, with only a sheetmetal chassis, the very modular construction shows obvious consideration made towards manufacturability and serviceability.