I posted this picture on the 'Dealer Select Thin Skin Strats' thread, because the discussion had gone in this direction, but thought it perhaps this is a separate discussion. I have a 60s RW strat and was curious enough to take nail polish remover to a small portion of the finish, in order to see what was under the nitro. There is indeed a base coat layer that does not appear to be nitro (it would have melted away on contact with the nail polish remover, were it nitro). The picture below shows the base layer. It has absorbed some of the colour from the nitro layer. The base coat is VERY thin, and soft enough to scratch with a fingernail, so I doubt it would affect the guitar tone in the same way as a thick poly finish. I would suspect it will wear in quite naturally over the years. BTW, I owned a Jeff Beck strat a few years ago, and chipped a piece of the finish off accidentally - it was as thick as the candy coating on an M&M - so I have seen how thick the 'regular' poly finish can be.