This Citizen 121F is a desktop electronic calcuator

Size (approx):  185mm x 255mm x 40-60mm (w,h,d)
Weight 1,250g excluding cable
 
Power: Mains (220-240V 50/60Hz, 4W) power only through a large three pin standard connector.
Display: 12 digit green VFD with additional symbol cluster on the left for memory (M), error (<) and negative (-) indicators. The display has upper commas for thousand notation (and unused lower ones).
Features: Standard four functions with percentages, square root, four function memory and register exchange.  Switches for constant, rounding and fixed/floating decimal.
Age: 1977
Manufacturer: Citizen Business Machines Inc., made in Japan. 
Comments: This late mains-only VFD desktop is larger and heavier than most and is very well built.  The viewing angle is a bit too low for my liking so you have to sit some distance away from it.  Logic is OK except for the strange handling of input overflow and archaic Reverse Polish Notation.

This calculator has a Serial number 511 06169 and was kindly donated by John Penn-Simkins

Thge above notes are taken with thanks from www.vintage-technology.info. For further information go to http://www.vintage-technology.info/pages/calculators/c/citizen121f.htm

Manufacturer: Citizen
Date: 1977

This exhibit has a reference ID of CH5105. Please quote this reference ID in any communication with the Centre for Computing History.

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