Buying guide
How to spot a fake bullion coin
Counterfeit bullion coins exist, and while convincing fakes are rare, a few simple checks catch the great majority of them. Genuine coins are struck to exact published specifications, and that precision is hard to fake in cheap base metal. This guide covers the checks any collector can do at home, and is meant as practical guidance, not a guarantee. For anything high in value, always buy from a reputable dealer and seek professional authentication if in doubt.
Start with the specifications
Every genuine bullion coin has a published diameter, thickness and weight. A fake almost always gets at least one of these wrong, because matching all three in the correct metal is difficult. Gold and silver are dense, so a counterfeit in a cheaper metal usually has to be the wrong thickness or the wrong weight to look right. Look up the official figures for your coin and check them. Our coin size guide lists the correct diameters for the coins we cover.
Measure the diameter and thickness
Use a set of digital callipers, which are inexpensive, to measure the coin across its widest point and its thickness. A genuine Krugerrand is 32.77 mm, a Gold Britannia one ounce is 32.69 mm, an American Silver Eagle is 40.6 mm, and so on. If the diameter is out by more than a fraction of a millimetre, treat the coin with suspicion. Fakes are often subtly too large or too thick to make the weight come out right.
Weigh the coin
Weight is the single most useful check. A precise scale that reads to a hundredth of a gram is ideal. A one-ounce gold or silver bullion coin should weigh its stated troy ounce of metal (about 31.1 g) plus any alloy, to the published figure. A coin that is significantly light is almost certainly not solid precious metal. Because gold is far denser than the base metals used in fakes, an underweight or oversized coin is a strong warning sign.
The magnet test
Gold and silver are not magnetic. A strong neodymium magnet should not attract a genuine bullion coin, and if you slide a coin down a tilted magnet, the eddy currents in real silver will visibly slow it. A coin that sticks to a magnet contains ferrous metal and is fake. The magnet test is quick and cannot harm the coin, though passing it alone does not prove authenticity, as some fakes use non-magnetic base metals.
The ping (ring) test
Real silver has a long, clear, high-pitched ring when balanced on a fingertip and tapped gently with another coin. Base metal gives a dull, short clunk. There are phone apps that analyse the tone. This test is a useful indicator rather than proof, and should be done carefully so you do not mark the coin, but a dead-sounding silver coin is worth a closer look.
Look at the strike and detail
Genuine coins are struck with crisp, sharp detail and clean lettering. Fakes often show soft or mushy design, slightly wrong fonts, weak or uneven edge reeding, or casting bubbles and seams rather than the clean surfaces of a struck coin. Compare a suspect coin against a known genuine example or a good reference photo. On coins with an annually changing design, such as the Maple Leaf, Panda or Kangaroo, check the year's design matches the real issue.
When to get a professional opinion
If a coin passes the home checks you can be reasonably confident, but no single test is conclusive. For valuable coins, or any you are unsure about, a reputable dealer or a professional grading service can authenticate it properly. The best protection of all is to buy from established dealers in the first place. Once you have a genuine coin, keep it in a capsule so its weight, edge and detail stay exactly as they should be for any future check.
More in our buying guides.