I just got an email from someone locally who I bought some slot cards from awhile ago (he's not a collector). Apparently he's found an old pinback from the Caesar's Boardwalk Regency in Atlantic City. His description indicates it's about 2" in diameter, has a medium-brown background with three cartoon like figures. Text says...

TRY US ON FOR FUN
Caesar's
Boardwalk Regency
Hotel Casino Atlantic City

Sorry but he didn't forward any photos but I'm sure he can if anyone is interested.

If anyone is interested, let me know and I'll give you his email contact info.

Bob