Could be legit. The shure cable is largely identical between series, so if he replaced the cable at any point then it would use the generic version rather than a 535 labeled one.

The bore could just have some wear, and I know from my own pair of shure iems that the gold connecter plating ends up rubbing off after a while since they freely swivel at that point, rather than being locked in place.

I'd say you just got a well-worn pair, my 2c