These covers don't prove anything for your chip ID but it does point out both the River Queen Casino & Holiday Casino were the same.
Both match covers are front strike with the same picture of the casino, phone number, manumark, safety and type of letter printing. The inside is also the same.

My unsubstantiated notes say the River Queen Casino never opened, although The Official U.S. Casino Chip Price Guide 2nd Edition says it was open from 1972 to 1973.

Harvey Fuller's Index doesn't list River Queen Casino. The Holiday Casino is listed and opened on July 2, 1973.