Coin Con Magic Trick (watch video).
A borrowed quarter is placed on the small pedestal. The pedestal is now covered. When the cover is lifted, the coin has simply vanished. Picking up the base a rattling noise is heard inside. The spectator thinks it's the quarter. When the base is opened, a small disc drops out with a message printed on it, “THANKS FOR THE QUARTER”.
Coin Con Magic Trick (watch video)