Ah, the good ol' days of Vegas... when a man could walk down the street and be handed "free play" tokens to pull the arm on a giant slot machine for nothing! The Westward Ho also used to hand these tokens out at the registration desk for free just to get a chance to invite you to stay on their property.
By handing this chip to the barker in front of the property you would get to play the promotional slot machine one time per day. The prize for a winning combination was usually a buck or two, but supposedly a jackpot paid $500 which was a huge prize back then! I bet it happened very, VERY rarely!
Or, knowing you were very probably going to lose anyway, many people would just keep the plastic chip as a souvenir. They often came with a small chain to use as a keyring, and some of ours at CasinoDecks.com still have them! This is a fun memento to recapture the spirit of the "pre-corporate" era of Las Vegas.