Hemmi of Japan made slide rules for a lot of other companies, especially Post. Those they sold themselves under their own brand name of Sun.
Hemmi 32, 4" Mannheim
This is one of my favorite slide rules. I bought this one on eBay because I liked the cut-out logo on the back. When I opened the package, I was stunned to see it was only 4" long! It is relabeled as a Post 1447M. This slide rule originally had a magnifying cursor, which has been replaced with a normal cursor, unfortunately. I've ordered a replacement from the Slide Rule Trading Co., but it hasn't arrived yet.
It was made between 1931 and 1933, and is listed in the 1932 catalog for $3.00.
Hemmi 34RK, 5" Mannheim
Post bought slide rules made in Japan by Sun/Hemmi and relabeled them for resale in the U.S. This one is a Sun/Hemmi model 34RK, relabled as a Post 1444K, and marked as "Made in Occupied Japan", which dates it pretty narrowly to 1945-1951.
Hemmi 40, 10" Mannheim
This is a very nice, but very basic, Hemmi 40 relabeled as a Post 1446. Hemmi stopped using the weird symbols in the upper corners in the 1930's and started using this "type A improved cursor" in that same decade, so this slide rule obviously comes from that decade.
The weird symbols and "quot +1" in the lower left corner, and "prod -1" in the lower right corner, were "mnemonic indicators" to help the user keep track of the decimal point.
Hemmi introduced date codes in 1951. The codes consist of two letters, the first representing the year (A = 1950, B = 1951, etc), and the second letter represents the month (A = January, etc). Not all of the 1951 slide rules received date codes, and slide rules in the 1970's often did not either.
Other indicators of age:
1895 - Jirou Hemmi founded. Slide rules are labeled "J. Hemmi".
1928 - Jirou Hemmi reincorporates as Hemmi Keisanjaku. Slide rules are labeled "Hemmi".
1927 - Model numbers changed from 1-18 to 20 and up.
1931 - Fredrick Post Co. starts selling Hemmi slide rules.
1937 - First inch on 10" slide rules is finely divided.
1930's - Stopped adding mnemonic symbols to slide rules
1940 - First inch no longer finely divided
1941 - S scale keyed to C/D scales on Mannheim slide rules.
1941 - No sales to Post because of WW2.
1945 - "Made in Occupied Japan".
1945 - Quotation marks around "Sun" dropped.
1950 - "Made in Japan".
1951 - Date codes introduced.
1957 - S scale keyed to A/B scales on Mannheim slide rules.
1976 - Production ends.
Be sure to check out Determining Dates of Hemmi Slide Rules at the Slide Rule Trading Co.
© 2003 W. E. Johns