Archie, that one is unusual all right. You have a lot more expertise than I do on AC chips but I'll point out a couple of things ==
The seller notes the presence of the "Baccarat" word on the chip, unlike the other $20's of this era. But there's another unusual element about the chip -- Instead of having a $20 denomination in 2 places as part of the "house" mold, there are a series of diamonds there instead.

It's my understanding that NJ Gaming required denominations as part of the house molds during that time. While Resorts, as the first to open, did have H&C mold chips for the first run, they quickly switched to the "house + denom" molds by their second run, about the time that Boardwalk Regency house molds came out.

The most likely explanation IMO would be if it was a PROTOTYPE chip for viewing & approval by the casino execs and/or surveillance folks. Never intended for actual play or for submittal for regulatory approval. Then (speculation) they decided against the "Baccarat" word and also included the $20's in the final mold.

With magnification, the chip looks legit. The cross-hatching appears untouched and the cross-hatch pattern is even consistent with the "Baccarat" lettering. That is, the ink seems to have been added before (not after) the cross-hatch stamping.

There are a few flea-bites nicks around the rim. It looks almost new, but not right out of the box new. Like it had a little wear over the years in a drawer or something?

I'm going with it being a legitimate prototype that was never in play. Just personal speculation though, as I have no independent knowledge.

What do you think?