Scotch & Soda
The performer shows a half dollar and a Mexican 20 centavo. They are easy to tell apart, because the centavo is copper and smaller than the half. Both coins are placed in a spectator's hand. The performer asks the spectator to put his hands behind his back, then hand you the half. The spectator easily locates the half. The performer asks the spectator what coin is left in his hand. The spectator will state it is the centavo. But when he brings his hand out and opens it, there's a U.S. quarter! The centavo has completely vanished.