[Arran]

 I don't know what happens to prototypes at all these days, but then again the electronics business is much different, radios and TV sets don't typically use LC circuits that need to be tested. I suspect that Micheal Feldt's 43-720 prototype may have been refinished, at least it looks that way, it has a rather flat open grained look with no decals over the controls. Whether it was intended to be a prototype or not I can't see why they would not have given that cabinet a the full finish treatment since it would not have taken any special effort for the cabinet shops to do this. To me it looks like the cabinet on the 42-720 was simply a stock cabinet that was taken from the production line, and modified, with those adjustment holes and what not, the cabinet on the 42-131T looks almost the same but with two fewer controls.
  I think that the original finish could likely be saved by using a similar method to what Bob Andersen used on his 39-30 cabinet, where the original lacquer would be cleaned, have any holes in the finish touched up with a brush, sanded, and then sprayed over several times. With regard to the escutcheon that does look home made, rather good compared to some I've seen, to me it looks like some sort of Mahogany like wood judging by the grain, which is a complete mismatch to the cabinet.
Regards
Arran