A suspenseful key test, in which a prize awaits the person selecting the correct key.
A transparent case is shown -- the magician opens it and inserts a bill that he says will be the prize. A padlock is presented, and a key is shown to open the padlock - 4 other keys do NOT open the lock. The bill is locked in the case by that padlock.
The magician then mixes the right key with the other four and puts them in a glass. Spectators from the audience mix them around so no one knows the location of the right key.
The five keys are then placed on the palm of the magician's hand and four spectators are each asked to choose a key.
One at a time, the keys selected by the spectators are inserted into the padlock, but none open it. The last key, the one left to the magician, opens the padlock. Everything can be examined.