Between .25 and .50 each at the most. Some early riverboats had tokens, so it was not a rare item. A small casino like that probably had minimum of $20,000 in nickel tokens (400,000 pieces) depending on how many nickel machines they had. Most casinos stored nickels in $100 bags, many casinos had a reserve door under the slot machine to hold an extra bag of coin. So if the casino had a 100 nickel machines easily 200 bags if not more. I don't believe the original Rock Island Casino was not big and most likely did not have over 100 nickels back then. Back then they were mostly reel slots and video poker and the denomination mix was way different from today's slots. Nowadays it's pennies with lots of pay lines and multipliers.

This is the kind of answer you get from a person that works in casino finance operations.