I asked Dr. Gaddy this same question on Nov. 1st, 2001 concerning the lockplates of a coin finished Beretta S3. His answer was:
"If the blemishes are not deep pits, you could probably help the appearance by polishing lightly with a mild abrasive. You might try Flitz polish which is good for polishing delicate metals. Other mild abrasives include common household cleansers such as Bon Ami, Soft Scrub, Comet and Ajax. I have listed these in order of increasing abrasiveness. You could also try using a common pencil eraser - this sometimes works very well on surface rust or corrosion.
I presume the lockplates were either color casehardened and have been polished or are one of the modern coin finishes"
JC
