Back in the day, this was a promotional given away by Allied. But it became an indispensible for many budding geeks/scratchbuilders lacking the math skills (me included). :nerd:

http://www.w7ekb.com/glowbugs/Calcs/alliedcalculator.htm

I just came across one earlier today while rummaging through my garage. Still in it's protective sleeve with the instruction sheet. Dated 1943, the same as yours.

http://www.videokarma.org/attachment.php?attachmentid=184722&d=1414460202

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Tarnation. That's amazing. And i used the heck outa that sucker too. One project was winding the coils for a 4-band regen set. Another was for transmitter buffer and final stage coils.

(The photos are an example i pulled off the web. But mine was identical, and had the 1943 copyright.)