Here’s a really nice and effective coin mystery using a spectator’s borrowed and marked quarter!
Effect: The performer takes the coin and places it into his pocket for just a second and immediately brings out a round colorful plastic box, which is handed to the spectator.
The spectator is asked to open the box and when they do they discover another box. This second box is opened to find a third box. When the third box is opened yet another box is discovered. Finally when the fourth box is opened the spectator discovers their very own marked quarter!
How the magician was able to introduce their coin into the innermost box in a matter of seconds is a very perplexing little mystery.
In a more advanced routine, the magician can actually make the spectator’s coin vanish first, and then remove the set of nesting boxes from the pocket and proceed as described above.