📖 How to tell a genuine coin from a fake and how to keep it

Fakes have been around almost as long as money itself. There are fakes made to be spent, sometimes collected for their historical interest, and fakes made to fool collectors. Here are a few simple checks you can do at home before buying a coin or having it appraised.

1. Weigh, measure, listen

• Weigh the coin on a precise scale and compare with weights recorded for genuine examples: a large difference should raise a flag.
• Measure the diameter: it should stay close to the average seen for that type of coin.
• A gold or silver coin has a distinctive sound, but learning to spot a doubtful one takes time.
• The magnet test: most genuine coins are not magnetic. A coin pulled by a strong magnet is a warning sign, although some modern coins contain a little magnetic metal such as stainless steel.

2. Examine the details under a magnifier

• On a genuine coin, the relief, letters and numbers are sharp and precise. A fake often shows blurred or uneven edges.
• Modern copies sold online or in tourist markets are often casts of a real coin: the details are less fine, with a suspicious weight and patina.
• Compare with photos of the same coin in catalogues or reputable sales.

3. Look at the patina and colour

• A natural patina forms over time and gives the coin a unique tone. A colour that is too uniform or too shiny may hide an artificial coating.
• Let the light play on the surface: the reflections on a genuine coin are subtle and varied.
• Some imitations are base metal covered with a thin layer of gold or silver. There are even kits to gild coins yourself.

4. Check the date and marks

• The year and mint matter a lot for rarity and demand, which is where tampering is concentrated.
• A common genuine coin may have been altered to pass as a rare year, or may carry a crudely added word such as "essai" (trial strike).
• Always compare several sources (catalogues, market prices, online examples) before believing in a rarity.

5. Do not clean it, store it well

• A shiny coin is not worth more: cleaning wipes out the patina and fine details and loses much of the value. Avoid chemicals, rubbing with a cloth or brush, and "miracle" baths.
• Keep it in a numismatic capsule or holder, away from light, humidity and large temperature swings.
• Avoid untreated wooden boxes (risk of oxidation), direct finger contact (grease deposits) and stacking (irreversible micro-scratches).

⚠️ Watch out for

• A coin offered far below its average value is almost always suspect.
• Older does not mean more valuable: some Roman coins, struck by the million, remain very affordable, while a 20th-century coin with a very small mintage can be worth thousands of euros.
• For a valuable coin, get an expert opinion and keep the paperwork. A certificate only carries weight if it comes from a recognised body (for example PCGS, NGC or the Société Française de Numismatique) and describes the coin precisely.

Sources : Godot & Fils (pièges des collectionneurs débutants) · Comptoir National de l'Or (authenticité des pièces)

Updated on Oct 6, 2026. These pointers are indicative and do not replace an expert's opinion: for a valuable piece, have it appraised.