Wonder Treasure Box (1507)

A bill or a currency note is borrowed from a spectator, folded, and dropped into a sealed clear crystal box through a slot on the top.
Hand the box out to the spectator, and he will not be able to open the box unless he learns the clever secret. But You can do it immediately under his nose.
Comes to you complete with step by step colored illustrated instructions. Carry it around with you and as the name suggests, leave your spectators wondering.