This little gems are from a small group in the files of the then Harman Kardon Industrial Designers. They are of course highly detailed and very likely one of a kind.
You get a total of 8 blueprints (7 are full sized, 2 are half size) in their original Shin-Shirasuna Electric Corp. folders (4 folders). At a later point Shin-Shirasuna apparently bought much of Harman Kardon’s audio division in 1979 and had already been providing the design work for the company.
Also included is an internal Harman Kardon HK 430 photograph.