I have an old engraved poker chip, Owl & Moon, that is counterstamped with the letter "R". Obviously done to prevent ringers, but I can't figure out how it was done. Most counterstamps I see are on coins. That's easy. Take the stamp and smack it with a hammer. But on a chip? Why didn't the chip crack? The only thing I've been able to come up with is heat. Kind of like branding. But, I don't see any evidence of burn marks on your chip. Anyway you have a VERY cool chip!