Ed, the answer to that one is, the government felt that any metal token might try to be passed as US money, where as you would think that anyone would realize that clay chips were not, so they did not put any special regulation on chips like they did on tokens.
In the very begining there was not much regulation on what the actual design was on tokens and whoever did the art-work casino or mint)just tried to make interesting designs.
Thus the "lucky bucks" and "cartwheels"
Hope this helps a little. Janice O'Neal