This is a sucker effect trick that everyone loves. In this effect the spectators feel that they have caught you, but you pull a fast one and prove them wrong.
A box with two doors and a gap between the two doors is shown. A coin or a similar flat object is placed in one side of the box and the door is closed. The audience is to guess behind which door the coin is. When the audience points to a particular door the box visibly tilted and the coin is visibly seen to have moved from behind the chosen door to behind the other door. Obviously when the chosen door is opened there is no coin to be found there. After some byplay and yelling and screaming from the audience you open both the doors and the coin vanishes from behind both the doors and reappears from a totally unrelated place.
The box measures around 5" x 2" x 1 1/2" and is ideal for a quarter for any flat object the size of an half dollar. You can make a card board cookie of the size of a half dollar and do a miniature version of the Cookie Chase routine with this mini money box.