Before 1940 Faber-Castell introduced
several slide rules for commercial use, that were based on the System
Rohrberg. This 342 is one of them. I have
not been able to figure out yet how it works. There are a number of
scales that resemble the later 22 -series slide rules (like the small
scales on the top of the rule), but others are very different.
The 342 also has an odd size; it falls in between
the 10" and the 20"slide rules.
There is not date stamp in the back, but looking
at some characteristics it should be dated between 1923 and 1935.
The rule has a faded stamp "Siemens
Aktiengesellschaft"in the well. |