You borrow a coin from a volunteer and mark the coin to ensure that it a unique coin. The coin is then vanished. You then reach into your pocket and hand out a plastic disc to the volunteer. The volunteer proceeds to open the disc and lo behold, there is another disc within it that contains another disc that contains a fourth disc. Finally when the volunteer opens the forth disc he finds his marked coin in it. There is no way you could have introduced the marked coin inside four nested discs, unless of course you knew magic. All the discs are of different colors.