Sun-Hemmi-Frederick Post 1441

One of the smallest, if not the smallest slide rule ever made, was fabricated in Japan for the American company The Frederick Post Co. since the early 1930's until the early 1960's; during the years 1942-1946 were not imported from Japan but fabricated in USA. These Mannheim 4 3/4 inches long (4 in long scales) slide rules were fabricated with bamboo coated with white celluloid, in two separated parts riveted to a thin metallic strip. I don't know the material used for the ones fabricated in the USA (wood? I have not seen one yet...).

The 1441's are usually sub-classified depending when they were produced: before 1942, labeled "Made in Japan" , and from 1946, labeled "Made in Occupied Japan" (until 1950), or simply "Japan" after 1950. But there is a very important difference between these models. The rules produces before 1942 had only four scales on the front face: A, [B, C}, D, and the rules produced since 1942 had the CI scale. At back of the slider all models had the scales S, L, and T. Another important difference is the inches-centimetres scales, the models fabricated before 1492 had a 4 inches ruler at the top edge, and a 10 cm ruler the bottom edge. The models produced after 1946 had only the 4 inches ruler.

Given the small size of the scales on these rules, they had usually a magnifier lens integrated in the cursor, but not all models had it.

References.

• Roos, Paul - Hume, Ted: Slide Rules of the Frederick Post Company. Journal of the Oughtred Society, Vol.9 No.2 Fall 2000. http://www.oughtred.org/jos/articles/V09.2_p37-46.pdf

• Roos, Paul - Hume, Ted: Post Slide Rule Archive. Sphere Research Corporation: https://www.sphere.bc.ca/test/post.html An extensive classification of Frederick Post slide rules can be found in this web-page.

• Roos, Paul - POST Slide Rule Cross Reference: Every slide rule sold by the Frederick Post Company of Chicago starting in 1903. http://srtco.us/PostCrossRef/Index.htm