Hobbies And Interests
Magnetic or Not?
If a coin is attracted to a magnet, it is not authentic. All valid coins are made from nonmagnetic metals such as gold, silver, copper and nickel. Many counterfeit coins are made from iron alloys that are drawn to magnets.
Measurement
According to the United States Mint, coins are made to exact size standards. The coin's diameter is easily measured with a ruler. The size of a valid coin should not vary by more than a fraction of a millimeter. See the coin size chart in the Resources section of this article.
Weight Check
Coins are also made to precise weight specifications. Weigh the coin on a sensitive scale made for coins, jewelry or postage. Valid coins should not vary by more than one hundredth of a gram. See the coin weight specifications in the Resources section below.
Surface Check
According to the Numismatic Guaranty Corporation, fake coins often have noticeable defects on their surfaces. Invalid coins that are made from casts of real coins commonly have a pitted or grainy appearance. They lack detail and can feel slippery to the touch. The surfaces themselves can be concave or convex instead of flat. These differences are often obvious when comparing fake and real coins side by side.
Edge Check
The edge of an invalid coin can have a small bump on it. This marks the spot where metal was poured into the cast used to make the fake. Sometimes this bump is sanded off. In this case there will be a small flat spot on the edge. The rim of a valid coin should feel consistent all the way around.
Sound Check
Valid coins make a distinctive ringing sound when dropped on a hard surface. Fake coins make a "thud" sound. Compare the sound of coins you know to be valid to the sound of the suspected fake. Do not do this test with valuable collector coins. Dropping a coin on a hard surface can damage a precious coin.