discoloration

[AtomicClock]

What do you suppose this discoloration is (from an online auction, with no chance of discussion with the owner, or further puctures)?

Olds Special

is_this_redrot.jpg

[Doubler]

I believe it's flux used in soldering the bell rim that didn't get completely removed prior to lacquering and was trapped under the clear finish, eventually causing the less-than-attractive result we see here. My first trombone had the same discoloration.