I've had a few times when I've gotten chips at the cage where, even though I said I didn't want any circulated chip (just pristine, unc ones), I got a few that had seen the tables. I always try to turn them on their side, and examine them closely, but still, a few slip by me now and again. Sometimes it's very difficult to tell while standing at the cage.

Your seller may very well have been underder the impression that this chip was unc, but as the scan shows, it has definately seen some use.