looks like it's seen some action. remember, the bullet has already left the barrel before the unlocking process takes place, and it will still lock up tight on the forward edge.
i assume it caused you no issues in the accuracy or reliability dept, as you only took it to the smitty for a site drift.
however, i would call and email those pics to glock, see if you can score a free barrel out of the deal. (who cares about non-matching serial numbers lol) won't cost you anything to try. if not, no worries. looks like normal wear to me.
I believe I will contact Glock about it...side note, lone wolf barrels will put your serial number on a new barrel for you (not that you couldn't stamp your own...)