I always start with files and go progessively finer until I can switch to sandpaper. My '63 is really old and has taken on a nice patina, but you can still see that it is nice and shiny. The steel parts have a soft sheen--kind of like old silver. The final step was to stroke the parts with a smooth steel rod. In the old days this was called "needling" and closes the pores in the metal. The result is an enduring polish and a very rust resistant finish.
You may be able to remove the Made in Japan stamping on the breech by draw-filing that flat. Depends how deep the marking was stamped in there. Good luck and never lose sight of the fact that this is supposed to be fun!