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mk 1 russomk 1 russo 00Technical Features
Manufacturer: Russian 
Year: c1968 
Info: 50 millimeters in diameter, The KL-1 is intended for performing trigonometric and mathematical operations: Multiplication / Division / Squaring / Extraction of a square root / Finding of trigonometric functions of a sine / Finding of trigonometric functions of a tangent / Finding inverse trigonometric functions /  Calculation of the area of a circle. Donated by my friend 
BohdanБогдан Ukraine )