Your comments, whilst valid, are not helpful. The only concern any potential purchaser should have is with the use of epoxy-potted circuit modules. (For the same reason why I would eschew any early Mark Levinson preamp.)

I'm sure the actual semiconductors used are still available, albeit expensive and rare. I use several items of audio electronics that are at least thirty years old without problem.

As Grant has suggested, it makes sense to test the gear first.