I am restoring a FH and the playfield is pretty wrecked. I think that way back in the day it got a damaged ball or something because a lot of the ball wear is down to the wood. However someone cut out a bunch of mylar and covered all the wood over (which likely saved it but it still looks ugly). I asked the guy I bought it from if he put them on and he said no and that he had owned it for 15 years. The cabinet is also pretty banged up and the back-glass was replaced with a piece of plexiglass so someone probably broke it. So none of that is so weird but when I started tearing into it to restore it I lifted up the playfield and the underside of the playfield was immaculate, super clean. I also noticed all these pencil marks where someone marked where the mechs sat. So someone years ago essentially restored the bottom of the playfield but not the top, or the cabinet or the back-glass. It is so weird to think about someone putting all that work to just the underside of the playfield. It has made me super curious about the history of the machine.

You might be right that someone started a restoration, got done with the underside and quit there.