The performer places a one dollar bill and a one hundred dollar bill on the table along with a quarter. The spectator is asked to spin the quarter on the table while the performer's back is turned. When the quarter comes to rest the spectator is asked to remember which side is up. The spectator places the magician's wallet over the quarter so it is completely hidden. Next the spectator is asked to hide one bill in each hand. All this is done while the performer's back is turned.
The performer turns around and removes 3 business cards from his pocket. He writes down something on each one and places one in front of each of the spectator's hands and one in front of the wallet. From this point the spectator opens his hands, revealing which bill is in which hand and THEY turn over the business cards proving both correct! But wait... remember the quarter? The spectator lifts the wallet revealing the quarter landed heads side up. Again THEY turn over the business card revealing the words "Heads Side Up."
This is ACCURACY.