Buying
Spotting Counterfeit and Altered Coins
Added mint marks, altered dates, whizzed surfaces, and how to avoid all three.
Reviewed July 2026
Counterfeiting follows premiums. Nobody bothers to fake a common coin, which means the coins most worth owning are the coins most worth faking, and the specific coins you have been taught to look for are the ones most likely to be false. That is an uncomfortable symmetry, and it is the reason this guide exists.
Three different frauds
They get lumped together and they are not the same thing. A counterfeit is a coin made outside the mint to pass as a real one. An altered coin is a genuine coin modified to impersonate a scarcer one. A doctored coin is a genuine, correctly identified coin whose surfaces have been tampered with to look better than they are.
The third category is the one that catches honest collectors, because the coin really is what the seller says it is. It has only been improved.
Start with the physics
Published specifications are exact, and a scale that reads to a hundredth of a gram costs very little. Counterfeiters routinely get the alloy wrong, and the weight betrays them.
| Coin | Mass | Diameter | Composition |
|---|---|---|---|
| Buffalo nickel | 5.000 g | 21.21 mm | 75% copper, 25% nickel |
| Morgan dollar | 26.73 g | 38.1 mm | 90% silver, 10% copper |
| Lincoln cent, bronze | 3.11 g | 19.05 mm | 95% copper |
| Lincoln cent, 1943 | 2.7 g | 19.05 mm | Zinc-plated steel, magnetic |
The 1943 cent deserves its own sentence. Copper went to the war effort, so for one year the cent was struck in zinc-plated steel, and steel is magnetic. A magnet is the fastest first test on any 1943 cent someone claims is copper, and on any 1944 cent someone claims is steel. Both stories are told constantly and are almost always false.
Added mint marks and altered dates
The classic alteration takes a common coin and gives it a scarce coin's identity. An S soldered onto a 1909 VDB cent. A mint mark removed to fake an error. A date reworked so that a Liberty Head nickel appears to read 1913.
On that last one, save yourself the trouble: only five 1913 Liberty Head nickels exist, all five are pedigreed, photographed and accounted for, two in private hands and three in museums. Reports of a sixth appear to be unfounded. Whatever you are looking at is an altered date. See nickels.
Added marks reveal themselves under magnification: the punch shape is wrong for the era, the position is slightly off, the metal around the base shows tooling, or the mark sits at a different height than a genuine example. Compare against a known-good photograph before you compare against your hopes.
Doctored surfaces
Whizzing is the crude version: a metal or wire brush taken to a coin to fake the look of mint luster. It leaves a directional shine that no genuinely uncirculated coin has, and grading services cap whizzed coins at AU-50 or lower.
Cleaning is the common version, and it caps a coin at MS-62 or lower. Overdipping, where a coin has been through dilute acid too many times and has had its luster stripped, does the same. Artificial toning, applied to hide problems or fake attractive colour, is the sophisticated version, and it is the hardest of all to call.
The rule that protects beginners
For any coin whose value depends on being a scarce date, buy it in a holder from a major third-party grading service, or do not buy it. Those services carry an opinion on authenticity, which is the part you cannot supply yourself. Counterfeit slabs do exist, so check the certification number against the service's online database before you pay.
A raw key date offered below the going rate is not a bargain. It is the shape a fraud takes.
The corollary, for anyone selling: do nothing to the coin. A well-meant polish makes an honest coin look doctored, and a suspicious grader is not a friendly one. See how to clean coins and how to sell coins.
Frequently asked questions
How can you tell if a coin is counterfeit?
Start with weight and diameter, because published specifications are exact and counterfeits often miss them. A Buffalo nickel should weigh 5.000 grams and measure 21.21 mm; a Morgan dollar 26.73 grams and 38.1 mm. Then examine the mint mark and date under magnification for signs of tooling. For anything expensive, a major grading service settles it.
What is an added mint mark?
A mint mark cut or soldered onto a common coin to impersonate a scarce one, such as adding an S to a 1909 VDB cent. Under magnification the added mark usually shows the wrong shape, wrong position, or tooling marks around its base. It is among the oldest frauds in the trade.
Is a magnet test useful?
For some coins, yes. A 1943 cent was struck in zinc-plated steel and is magnetic. A 1943 cent that is not magnetic, or a 1944 cent that is, deserves expert examination rather than excitement, because both are heavily counterfeited.
Does a slab guarantee a coin is genuine?
A holder from a major third-party grading service carries that service's opinion on authenticity and grade, which is why the market values slabbed coins. Counterfeit slabs exist, so check the certification number against the service's online database.
More on buying
The Coin Register is an independent educational resource. It is not affiliated with the United States Mint, the American Numismatic Association, any grading service, any dealer, or any site previously published on this domain. Nothing here is an appraisal, a price quote, or investment advice. Coin values change constantly; check a current price guide and a reputable dealer before you buy or sell.