The name of this effect is a little misleading because what you receive is not a real playing card but actually a plastic plaque with gold colored recessed pips. Because of this the card is very durable and should last you for many years with proper care.
Effect: Make one playing card appear to have many different values!
First you show that the card has one diamond on one side and four diamonds on the reverse side. When you show the sides again, one side has three diamonds and the other side has six diamonds!
Easy to do! Great trick for the beginner! Great for giveaways after your show!