Counterfeit Detection
Why authenticity comes before grading, the quick physical checks anyone can do, how to recognize cast and transfer-die fakes and altered coins, the risk of fake holders, and when to send a coin to the experts. For protection only.
Authenticity comes before grading
In plain English
The first question about any coin is not 'what grade?' but 'is it real?' A counterfeit has no collector grade, and grading services authenticate every coin before grading it.
Going deeper
Services verify genuineness using weight and diameter, die-diagnostic comparison under magnification, and surface/luster analysis (and instruments like XRF). A coin judged not genuine is returned as a no-grade, never encapsulated as authentic.
Sources: Numismatic Guaranty Company (NGC) · Professional Coin Grading Service (PCGS)
Quick physical checks
In plain English
A few simple checks catch many fakes: compare the coin's weight and diameter to the known specification, use a magnet where appropriate (genuine U.S. silver and copper coins are not magnetic), and look closely at the edge for seams or the wrong reeding.
Going deeper
For example, a genuine bronze cent is non-magnetic and weighs about 3.11 g, while a copper-plated steel fake is magnetic and lighter. Edge examination can reveal casting seams, added mintmarks worked from the edge, and altered surfaces.
Sources: Professional Coin Grading Service (PCGS) · Coin World
Cast counterfeits
In plain English
A cast fake is poured into a mold rather than struck. Tell-tale signs are a faint seam around the edge, a rough or pitted (porous) surface, soft mushy details, and a dull thud instead of a coin's ring when gently tapped.
Going deeper
Casting can't reproduce the sharp, flowed detail of a struck coin, and trapped gas leaves porosity. Combine visual inspection with weight, diameter, and (professionally) composition testing.
Sources: Numismatic Guaranty Company (NGC) · Professional Coin Grading Service (PCGS)
Struck fakes and altered coins
In plain English
More dangerous are struck fakes made from dies copied off a real coin (transfer dies), which repeat the same marks on every fake, and genuine common coins altered to look rare, added or removed mintmarks, altered dates, and tooling.
Going deeper
Transfer-die fakes show 'repeating depressions' (the same marks in the same spots across examples) and often soft detail. Altered coins show tool marks, color/luster mismatches, and wrong digit or mintmark shapes versus genuine references.
Sources: Numismatic Guaranty Company (NGC) · Professional Coin Grading Service (PCGS)
Fake holders, and when to consult the experts
In plain English
Counterfeiters also fake the plastic slabs of grading services. Treat an unbelievable bargain with suspicion, and when in doubt, send the coin to a trusted third-party service or a reputable dealer rather than guessing.
Going deeper
For anything valuable or uncertain, professional authentication is worth the fee. The major services (PCGS, NGC, ANACS, CACG, ICG) and the ANA exist precisely to settle questions of authenticity.
Sources: Numismatic Guaranty Company (NGC) · Professional Coin Grading Service (PCGS)
Key terms in this lesson
Counterfeit · Cast Counterfeit · Transfer Die Counterfeit · Altered Date · Tooling · Re-engraving · Mintmark · Details Grade