Woah, why spend the money on a bill validator when you can just use a 950-984 coin unit? Takes tokens and quarters. It's what we use.

Imonex V9 series is what we use, but they sell ones with lockout solenoids and such. 950 means it takes quarters, and 984 is the diameter (.984 ), in this case, of the tokens used. I'm not sure where you would get smaller amounts of tokens. We get 'em in the 1000s, but they're custom minted. I think your best bet is to just call imonex and talk to them about what you need, and see if they have a recommended place that sells generic tokens in lower quantity.

A radio interface? That's unique. How will that work?

We never had a problem with people buying tokens off Ebay. Even with the local university having the same token with a different image for free play, I'd say maybe a dozen of the tokens from the university ended up in the arcade, in the 5 figures we've collected from there.