S 42 question

Looked at a 1939 S 42 today and have a couple of questions-piece is excellent+ in and out but the side plate has some blotchey looking reddish discoloration-also the # on the side plate "09" looks like the rest of the #'s on the gun but has a faint circle surrounding it-on the inside of the side plate there is a similar mark opposite the outside-not a dent, tho-I have not fooled much with lugers in the last few years and am unfamiliar with the current fakery and remarking techniques.

Wondering if this is a faked #. Gun is real nice with a real nice 42 holster-one unmatched mag no tool-what is ball park figure on this piece?

Mike P