What are these dents on the slide handles and braces?

[berntd]

Hello,
How do I post a picture?
Anyway, I have here a Yamaha YSL-354 made in Japan.

I noticed big, deep dent like indentations where a player would hold the trombone, around where the slide screws to the bell.

It looks like dings made by blunt hammer blows.
The brass really has round crater like indentations.
But all around that area so not doable by hammer as such. It is where the laquor is gone.

Is that loss of material due to corrosion?

Is this a common issue with trombones or what is going on?

Regards
Bernt

[Elow]

Sounds like pitting. It’s where acids from your hand slowly eat away at the material of the slide. Not common, but definitely not unheard of.