Hi Hauke!  Nancy Fratti here.

The only way I know to get rid of rust spots is to polish the cylinder,
thus removing the rust.  Then the cylinder should be lacquered to seal the
surface.  But, in order to do that you will have to remove the cylinder!

In order to remove the cylinder you have to remove the spring, and, to be
safe, also remove the governor (and you should remove the comb so you
don't accidentally damage that!).  Do you have a lot of spare time???

"Rust removers" will not work -- and anyway, you'll damage the rest of
the mechanism if you don't remove the cylinder.

If the rust is bad enough, or left unattended, it will eat-away at the
pin where it enters the cylinder, thus weakening it, and someday the pin
will break off!

I wish I had some better news for you!  Have a GREAT Holiday!

Nancy Fratti -- MusicBoxLady@Juno.com

P.S.  Jody & Robbie,  Many thanks for all the information and people
you've brought together with MMD.

 [ And thanks to you, Nancy, for sharing your music-box wisdom with our
 [ readers around the world.  I hope your generosity is rewarded by
 [ pleased customers and new friends!  --  Robbie