Yes, it is 10k gold. When this $100 token was made, the US$ was worth a lot more and there was much less than $100 worth of material in the token.

Not every casino's $100 slot tokens had gold centers. The Gaming regs only reguired a gold surface so that coin rejectors in the machines could detect genuine ones. Caesars Palace (used to be) a class act and used a gold alloy, not plating.