The 4138 Morrison Radio Engineer's Slide Rule was a special slide rule for solving problems in radio engineering in the time frame of 1939. It had a set of 9 scales specifically for radio proprogation.
The 4138 only appeared in the 1939 catalog of the catalogs available.
The following scan is the description page of the instruction manual for the 4138. The manual is from the collection of Michael O'Leary.
