I have an old pre-serial chrome over brass Supraphonic 400.
Threre are small dents into the shell: one is in a panel and caused accidentally and the others are situated under the mounting feet of strainer and butt, so I think at the Ludwig factory or later by someone the mounting screws of strainer and butt were tightened too hard and so made strainer and butt pushing into the shell.
How can I hammer out these dents without dammaging the shell on the inside and causing no new dents from the inside towards the outside?