Since the vast majority of TOS props that are brought to market are fakes, it's only natural to ask whether or not this one is real. I've done some research on these in the past and I can tell you that this is the real thing, in my opinion.
Two types were made for the episode – static and ones that lit up. This is a static, non-lit version and has all the right details including font style and size, shape, necklace detail, miscellaneous details and age. Can this piece be faked? Of course. ANYTHING can be faked. But in this situation I see no indications that that's the case, and every indication that it's real.
I'm not a buyer, but If I was, I'd go for it with no hesitation. The best thing about the auction is that the seller has given a rather questionable story which means lots of buyers will steer clear. Don't let bad story-telling get in the way.