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.
We do not believe these initial designs were ever produced.
You get 3 blueprints, one for each number, in their original Shin-Shirasuna Electric Corp. folder. 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.
Among the cache’ of original H/K blueprints in this estate these (and a few others that involve pieces we believe were never produced) are certainly the rarest though that is a relative term as they are all likely one of a kind.