Did my 77 P bass in about 1979, what a b'stard to do, under the sunburst was some sort of polyurethane? filler, clear and rock hard (fullerplast?) However the wood was stunning when stripped. Amazingly (IMO) I got a really good finish afterwards even though DIY. Bass had bad accident later, broken neck, sold bits and was quids in. For 70s Fender, was well built but not great setup. Once sorted, no complaints.