jack,
I am not as worldly knowledgable as others on the history of the P/M, but IMO that looks like a NOS unit that has been sitting in that box for many years.
- It has a 1st generation acc ball on it that has a history of premature failure.
- It has a mastercylinder that looks like it just about rolled off the showroom floor. A tad of corrosion, but alum will do that in time. It will wipe right off.
- The motor leaves a lot to be desired, but it is probably new (just old) and for whatever reason was not annodized properly. Sitting on a garage shelf for 15yrs in an unsealed box would allow moisture to rust it.
- That hose is in a hell of a lot better shape than any I have ever seen.
- It has the right pressure switch on it.
My guess is that GM's original mfg rejected it at QA inspection. Probably for the motor casing being improperly annodized. It was probably set aside and forgotten. It never left the shelf until the compony folded and it got into someones hands. Now it's in yours. I agree, you paid too much money for it....however much it was.
If you want to put it back into service, you better get it into knowledgable hands that can properly break it down and check the internal orings. Most orings have only got a shelf life of about 5 years (+/-) depending on matl and if they are not put into service.
HTH,
Z
edit: I just saw the the selling post. Price wasn't too far out of line, but still too much considering what you will have to do to make it streetable.