You borrow a coin (for instance 1 ) and you ask a spectator to sign it.
You place it between two plexiglas plates bordered by 4 rubber bands.
You give the whole material to a spectator for examination. He will confirm that the coin is trapped.
Then you put the whole material under a napkin.
Suddenly the coin vanished. The plates are given to the audience : the coin is no longer between them.
You can fin it anywhere you want.
An automatic and very inventive pocket trick.