Regardless of who altered the chip, the seller is responsible for what he is selling. The chip was obviously not used in the casino, although the seller claims it was. To me that amounts to fraud. The seller may just be mistaken and is not willingly trying to defraud anyone, but my argument is that the seller's intent is not material. Regardless of whether the seller knows what he is doing or not, someone buying this chip based on the seller's claims is a victim of fraud.