Scotch and Soda with Brass Bang Ring
Half Dollar and (replica) 20 Centavo coin are given to spectator to hold behind his back. Magician asks for the half dollar which the spectator successfully hands over. Next you ask for the 20 Centavo coin. When the spectator opens his hand he finds that Mexican Coin has changed into a quarter and he can examine both coins to his heart's content. Again, the only reason this is such a straight-forward miracle is due to the precision machining of the coins. Here's one you'll really use. Complete with bang ring. Easy to follow routine included.