I too believe they were prototypes and never in play. I have a similar one from Caesars on my website, a green $25 with NO inlay! If they were in play at MGM I probably would have gotten one as I did see the Dean Martin show once at the old MGM and remember full well Frank at Caesars. NEVER saw them on the tables when they appeared at either casino. That doesn't mean they never were used but I seriously doubt it.