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 6 blueprints in their original Shin-Shirasuna Electric Corp. folders (2 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 A 402 and T 403 photographs (4) and and internal HK letter regarding the design along with notes on the back.