The oldest (probably acquired in middle school) is a Yamaha B-flat, which received a DEEP karate chop to the bell bow.
I did a darn-nice job (hey: NO filing/NO sanding...and it was thin-from-the-factory AND pitted, so those strategies would have been EXTREMELY ill-advised) removing the 40%-deep dent, but - resulting from the karate chop (plus the age/wear factor) were some little cracks.
Rather than ordering a new bell or installing a horrible patch, I floated a layer of silver braze material over the area.
I carefully contoured it (sort of like a dentist fits a replacement crown - except I used a needle file and sandpaper, rather than a drill), and ONLY filed and sanded the silver braze material (feathering the edges into the bell) - followed up by some conservative buffing.
The ancient clear lacquer had darkened over time, so I heated the area (darkening the polished brass) and hit it with some lacquer with a darkened-appearance tint. This tint also hid the "white" color of the silver braze material in the repaired area.
The low spot (shown in the reflection) is a pit (wear spot - not a dent) just below where I mounded up the silver braze material. Thus, it's accentuated.
The straight cylindrical portion (leading into the #1 casing) was also wonked, but - well... - no cracks.
(Bending a bow into a bell naturally is going to make the outer circumference thinner - due to stretching.)