How to spot a fake silver coin

Weight and size

You need a scale that reads to 0.01 g and a caliper. Compare the coin with the official figures below. A worn coin can be slightly light. A coin that is clearly off is a warning sign.

Coin	Weight	Width
Mercury dime, 1916 to 1945	2.50 g	17.9 mm
Washington quarter, 1932 to 1964	6.25 g	24.3 mm
Walking Liberty half dollar	12.50 g	30.6 mm
Morgan dollar	26.73 g	38.1 mm
Peace dollar	26.73 g	38.1 mm
American Silver Eagle	31.103 g	40.6 mm

Source: US Mint coin specifications. Silver Eagles are 99.9% silver; the older coins are 90% silver and 10% copper.

The magnet slide test

Silver is not magnetic, but a strong magnet still acts on it. A moving metal that is a good conductor makes small electric currents that slow it down. Tilt a smooth board or a plastic ruler at about 45 degrees, tape a strong magnet (neodymium works best) along it, and slide the coin down next to the magnet.

• A real silver coin slides down slowly, as if it is dragged.
• A clad or base-metal coin slides down faster.
• A coin that jumps to the magnet is steel or iron, and is not silver.

Compare with a coin you know is silver, such as a 1964 quarter, and a coin you know is not, such as a 1980 quarter. The test only compares coins. It does not give a number.

Density

Density is weight divided by volume. Pure silver is 10.49 g per cubic centimeter. A 90% silver coin, which is 10% copper, works out to about 10.3. Copper is 8.96 and nickel is about 8.9, so a copper-nickel clad coin is lighter for its size, and many fake metals are lighter still.

1. Weigh the coin dry. Call this A, in grams.
2. Put a cup of water on the scale and set the scale to zero (tare).
3. Hang the coin from a thread and lower it into the water. It must be fully under water and must not touch the sides or bottom. The scale now reads the weight of the water the coin pushed aside. Call this V. One gram of water is one cubic centimeter, so V is the coin’s volume.
4. Density is A divided by V.

A Silver Eagle should give about 10.5 and a 90% silver coin about 10.3. A fake plated with silver usually gives a clearly lower number. The reading is small (a Morgan displaces about 2.6 g of water), so use a scale that reads to 0.01 g and keep the thread thin.

Altered and added marks

Some real silver coins are not fakes of the whole coin. They are common coins changed to look like a rare date or mint mark. A mint mark can be added to a plain coin, or a date can be changed. These coins are worth the price of the common coin, not the rare one.

• Look at the mint mark with a loupe. An added mark often sits on a flat or scratched patch, or has edges that look different from the surrounding metal.
• Compare the shape and size of the mark with a picture of a real coin from the same series. The coin pages show the date and mint mark for every issue.
• Be careful with any key date that is offered at a price well below the guide value.

Before you buy or sell

A coin worth hundreds of dollars should be checked by a person. Take it to a dealer with a good reputation, or send it to a grading service, which checks authenticity as well as grade. Buy valuable coins from sellers who take returns. For coins that are only worth their metal, the silver check and the melt calculator are enough to see what you have.