The silver solder gave me an idea: I've tried to fill the rubbing marks with tin drops. It doesn't work, the tin simply doesn't bond to the aluminum alloy. I bet that this is related to insufficient heating, but as advised earlier, I prefer not to heat up a 30-year old MTB part.There was such a thing as metal filler for cars. No idea if it would match the alloy crown, but if you sanded it all it would have the same grain/texture so might look ok.
Silver solder?
Stickers.