Two-Headed or Magic Coins
If you ever find a coin that has two heads or tails, you may first think that you have discovered an exotic mint error. While they appear to have two heads or two tails, these coins aren't made that way at the Mint.
In reality, you can purchase two headed or two tailed coins at a magic shop. The technique in making these coins involves two coins. One is hollowed out to the rim, the other coin has its rim and reverse removed. The second coin is inserted into the first so that the seam between the two is at the rim and virtually unnoticeable. There is absolutely no evidence of tampering on the edge.
These coins are often underweight since they are partially hollow inside. They also fail the "ring" test (balance a coin on your finger and tap it with a pencil, it should have a bell like quality. Coins that sound "dead" are not a continuous piece of metal so the sound stops at breaks between the joined pieces).
A good many of these coins are spent by accident because they look just like regular coins. If you find these coins they are worth more than face value.
So take a trip to a magic shop in your town. That's where you can find all kinds of illusions and tricks for a magic show or just some slight of hand to impress your friends with.
Magic shops charge a large premium for these special coins.