AboutMyCoinHow can I tell if my coin is fake?
Weigh it and measure it first, because a counterfeit that matches the design rarely matches the specifications to a tenth of a gram. Then check the magnet, the edge, the sound and the mint mark, and on anything worth four figures have a grading service settle it rather than the internet.
Weight and diameter first
Every coin was struck to a published specification, and a counterfeiter has to match the design, the diameter, the thickness and the density at once with metal that costs less than the original. Most do not try. A scale reading to a hundredth of a gram and a pair of callipers settle the majority of cases in under a minute.
Compare against the specifications on the coin’s own page in the coin value catalogue, not against another coin in your pocket. A fake that is 5% light is obvious against a published figure and invisible in the hand.
The magnet and the edge
No United States silver, gold, copper or copper-nickel coin is magnetic. A coin that responds to a magnet is plated steel, and the question is over. A strong neodymium magnet held near a real silver coin produces a faint drag rather than attraction, which is a different effect and takes practice to read.
Then look at the edge for a seam, for a copper stripe where none belongs, and for reeding that is uneven or soft. Cast counterfeits show a line where the two halves of the mould met; struck ones show reeding that does not run cleanly to the rim. The same edge check tells you whether a coin is silver at all: see how can I tell if a coin is silver.
Details counterfeiters get wrong
Compare the font of the date and the legend against a known genuine example of the same year, at magnification. Digits that are slightly the wrong shape, letters that are mushy, a design whose fine lines are rounded rather than sharp: all are signs of a coin that was cast or struck from dies made by copying a coin rather than by the mint.
Look hardest at the mint mark, because adding or altering one is the cheapest way to turn a common coin into a scarce one. A mark that sits at the wrong angle, in the wrong position for that series, or on a patch of surface that looks different from its surroundings is the classic alteration, and it is the one worth knowing for every series you collect.
When to pay somebody
When the coin is worth enough that being wrong costs more than the fee, and when it is a key date in a well-known series — those are the coins that are faked, because faking a common coin makes no money. The grading services authenticate as part of grading, and the holder is what lets the next buyer accept the verdict without repeating the argument.
Nothing you do with household chemicals should be part of this. Acid tests damage the coin, and cleaning it destroys value on the genuine article while proving nothing about a fake. Should I get my coin graded covers what the service costs you in return.
Related questions
More on grading and condition
Condition is the largest variable in a coin’s price and the one most easily destroyed at home.
Coin Grading and Condition collects every question on this topic in one place.
Not an appraisal. AboutMyCoin estimates from published specifications and does not authenticate or grade coins.