Coins - Authentication

Separating out frauds or fakes from genuine (even error) coins requires experience and ongoing research.

The first test to apply is a visual inspection. Look at the rim. If it isn't fluted properly (the 'roughened edge' of a coin), it's a fraud, assuming it hasn't been worn by wear.

A visual inspection can immediately show up any blatant fake. Any two-headed coin, for example, is not an error but a fake. That can be verified by holding a genuine coin in one hand and tapping it with another of the same denomination.

The two-headed fake will have a dull thudding sound, as a result of the glue bonding the halves of the fake together. A genuine coin will give off a metallic twang. That, and the fact that no legitimate mint ever produced a two-headed or two-tailed coin, provides proof.

More sophisticated tests are sometimes easy to apply for more difficult cases. A genuine coin is made of the right type and density of metal. A silver dime is made of silver, a gold dollar is made of (at least) 14kt gold. Coins not made completely of the right metal or alloy will differ in weight and density.

That means some simple tests can determine their lack of authenticity, if they're frauds. Each genuine coin will have a standard mass, easily measured with a balance.

Each metal or alloy has a standard density that can be measured by simple tests devised as far back as Archimede's time 2,500 years ago.

If the coin is electroplated, it will fail the weight and/or density tests. Some care is required, though. Mints have been known to change metals from time to time. The discontinuance of all silver dimes in 1964 is a famous example. The 1982 Lincoln penny, though is a less obvious example. Some were zinc, others copper. Copper cents have a mass of 3.11 grams, zinc cents were only 2.5 grams.

Zinc and copper coins also have a different sound when dropped on a hard surface, such as a tile countertop. Describing the difference is impossible, but testing some coins will quickly educate your ear to the difference.

For more valuable coins, collectors will want to take advantage of a professional grading service, such as PCGS (Professional Coin Grading Service) or NGC (Numismatic Guaranty Corporation). Dealers, too, frequently offer grading services though sometimes they outsource the job to one of those two companies.

With the array of technology available today, it's very difficult to pass a fraud off successfully. The effort needed to accurately produce a high-value fraud that would pass those tests would be so expensive that it's worth it only in the case of very rare and valuable coins.

But computerized catalogs and the widespread knowledge of coins at that level means it takes only a few minutes to find out the current status of most of them. The ownership and history of the top 100 coins in value in the world are pretty well cataloged by now.

For other coins, part of the fun of collecting is doing the research to evaluate their worth. Computers have made that easier, but no less exciting.

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