Does anyone know what type of coating would be found on an N.O.S. GM mirrored T-Top? I recently found a factory replacement, still in the GM box, from 1979 and it has a brownish coating applied to the outer side of the top. It must be some type of preservative, but it's not a plastic film that can be peeled off. In case soap and water doesn't do the trick, I was given a chemical from a GM parts dept. that they used to remove the coating on vehicles that arrived by transporter ("Transfilm Remover"). I just want to be careful since this is a rare factory replacement top (M1131 mirrored/blue).