of availability are estimates. Many models did not appear in the
Hemmi catalog until several years after they were officially announced;
others never appeared in a Hemmi catalog but dated specimens are known; for
some models, all I have is a picture from an auction site.
Abbreviations used are
Made in Occupied Japan
World War II
End of (Hemmi Slide Rule) Business
Hemmi Date Codes
Most Hemmi slide rules manufactured after 1951 have a code indicating
their date of manufacture engraved in very small un-inked letters. The
code is in the form "YM" for bamboo rules or "^YM" for all-plastic rules.
The first letter represents the year with "A" = 1950. The second
letter indicates the month of manufacture with "A" = January. Thus,
"TK" or "^TK" indicates November 1969.
Usually the date code is near the lower left corner of the rear of the
rule but it can be almost anywhere. Because the letters are small and
un-inked the date code can be hard to find--you may need to examine the
surface with a magnifying glass in raking light.
Although the coding system started in 1950, most rules manufactured in
1950 or 1951 do not carry a date code. The earliest date code of which
I am aware is "AL" (December 1950). Theoretically, the date code system
applied through "ZL" (December 1975) but Hemmi became inconsistent about
applying them in the last few years of their slide rule business. "X,"
"Y," and "Z" date codes are rare.
For a guide to estimating dates of manufacture of Hemmi slide rules click here.