This is an early variation No. 50π aka 50pi (or 50/1pi) of the basic Sun Hemmi 50 (later 50w and 50p) slide rule. This 50π version has the folded scales CF and DF at π, together with the information on the back, specially aimed for calculation for circles and spheres. Only made from 1936 un till the second world war until occupation, so let’s guesstimate this one is from ca, 1938. The sun is written as “sun” which also indicates this early pre war period.
This slide rule and case, as wel as the metal frame of the cursor have the “Sun” Hemmi logo, so all original. . It has scales on both sides of the slider and the metal curser with glass insert has 3 hairlines from top to bottom. The slide rule and curser are complete and everything is in good condition with clear signs of use and age. The cardboard container is also complete, but is missing patches of black paper. This slide rule is a little smaller and measures ca. 28,5 cm or 11 1/2 inches. Check out the attached video on how to operate a vintage slide rule!
