I never knew these were called soda or restaurant checks. I always thought they were just embossed numeral checks. It did seem weird to have so many denominations for poker (or anything, actually): 15, 20, 25, 30, etc. A book, "Tokens and Medals," by S. Alpert and L. Elman says these were used for a glass of soda or general merchandise, or paying for meals, good for a cup of coffee, or for internal accounting (due waiter or cashier (??)).

Robert