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.