"The Polyphase Duplex Trig"
by: Lyman Kells, Willis Kern, and James Bland
This is a short preview of the manual for identification purposes. Complete scans will be provided when time is available. If someone has a particular need to view the entire version of this manual, please email me and I will put it first in my list to finish. Email address
There are two versions presented here with a 1939 copyright date. The first with the orange cover was probably the original printed in 1939. The second has different cover and intro sheets while the text after page 1 is identical between the two. Due to the green cover on the second one it is assumed it was printed in the 1950s. The 1939 version is the only one to have ads for other slide rules in the rear.
The first printing:
The 1950s printing:
This manual is from the collection of Clark McCoy
The scans of this manual were provided by Clark McCoy
These web pages were produced by Clark McCoy