I know I said I wasn't going to mess with it, but I couldn't resist doing a little cleaning test on the tuner cover plate.
First I tried Naval Jelly with some success, but then I tried Rust-oleum rust stripper. Wow - it instantly turned from yellow to brilliant silver

Just like a TarnX commercial.
I think I just might have to polish the whole chassis if it's really that easy.
I took a peek under the chassis. Nothing too bad. Just the usual oozing wax caps and one has already blown. The seller had turned it on several times
She was about to plug it in again when I came to pick it up.

I nicely pointed out the hazards of doing that.