Thanks Peale, thats saves me a lilttle cash. In fact I would prefer it that any coin put in would register, I can use it a HUGE piggy bank then 
Well, not ANYTHING will register. The first catch on the way down thru a coin mech is a rocker that tests whether the thing you've dropped in is anywhere near the size of a quarter/token. If you use a dime, nickel or penny, it will probably just drop right thru rather than rocking forward, and will end up in the return slot.

Here's a look inside. There's actually a tab that the coin hits first that tests for thickness (not visible behind the token) to make sure the coin is not too thick. This is adjustable with a screw on the outside of the mech.
If the token passes, then it hits the brass rocker, which tests the token for minimum diameter. If the coin is too small, it just falls thru and drops into the return slot. If the token is big enough, it will rock forward toward the white post above. The rocker also seems to be a test for weight as well -- an aluminum or plastic token of the right size will not rock forward, and must be rejected manually to clear the mech.
If the token is the right size and weight, it will rock toward the white post, which checks for maximum diameter. This is also adjustable by rotating the white plastic base of the post. If the coin is too large, it will lodge against the post and must be rejected manually. If the coin is not too big, it will continue to rock forward, dumping out of the rocker and rolling down the mech to the final challenge: the magnet.
The magnet (next to my thumb above) checks for steel slugs. Steel will stick to the magnet, and again must be manually rejected. The coin reject button basically opens up the entire mech and allows any jammed coins to fall thru and into the return slot, while simultaneously sweeping any remaining coins with a metal arm.
If you want to use your cab as a piggy bank, you'll need to make a modification -- i.e. put something underneath the rocker (like a screw) that blocks smaller coins from dropping thru, whole not interfering with the larger coins. I've tried this before with varying results. After a lot of tweaking, I was able to get all US coins to go thru about 75% of the time. A lot of times you'd have to reject the coin or slam the coin door when dimes got stuck. Also, dimes are so small that about 50% of the time, even if they make it thru the mech, they'll just drop right past the coin switch without hitting it...
