A Mystery Box Restores The Torn Pieces of A Chosen Playing Card

Here's a demonstration of what some say is a classic magic trick, known as the 'Torn & Restored Card'. It has certainly been around for quite some time.
The magician tears up a chosen card, and retains one corner.
The pieces are placed in a small box and the magic word is uttered.
On opening the box, the card is seen to be restored, apart from the one corner that was retained in the audience member's possession.