This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Procure a pill box and a clean cork. Cut two disks from the cork to fit in the box, and fasten one of the pieces centrally to the inside bottom of the pill box with glue.
To perform the trick, put the loose disk in with the one that is fast, and then open the box to show both corks. Close the box and in doing so turn it over, then open and only one cork will be seen. Be careful not to show the inside of the other part of the box with the cork that is fastened. - Contributed by Fred B. Spoolstra, Yonkers, N. Y.