Counterfeit Detection: A Field Guide for Buyers Without a Lab

Bullion counterfeiting is a real industry. Tungsten-cored fake gold bars, copper-cored fake silver coins, and entire fake mint-packaged sets circulate through online marketplaces every day. The good news: every counterfeit has to lie about something, and the lies are detectable.

The four-test routine

Every coin or bar entering your stack should pass four tests before you keep it:

• Weight: jeweler's scale to 0.01g accuracy
• Dimensions: caliper for diameter and thickness
• Magnetic: neodymium magnet (catches steel cores)
• Ping: resonance test (catches dense-metal cores)

Weight is the single best test

Counterfeiters cannot match weight, dimensions, and metallurgy simultaneously. Tungsten matches gold's density almost exactly (19.25 vs 19.32 g/cm³), which is why tungsten cores are the gold standard of fakery, but tungsten cannot match silver, platinum, or palladium densities. For silver coins, a digital scale is conclusive. For gold, weight catches everything except tungsten cores.

The ping test in detail

Balance the coin on a fingertip and tap it gently with another coin or a wooden pencil. Genuine silver rings for 3-5 seconds at a high pitch. Genuine 22-karat gold rings for 1-2 seconds at a slightly lower pitch. Tungsten-cored fakes produce a dull, short tone because the core dampens vibration. There are smartphone apps (CoinTrust, Bullion Test) that analyze the audio frequency spectrum to confirm.

"In 30 years, every fake I have caught had at least one anomaly: weight, ping, or dimensions. Counterfeiters never get all three perfect at once." - precious metals fraud investigator, Interpol working group

Magnetic slide test

Tilt a slick surface (a piece of glass) at 45 degrees and slide a strong neodymium magnet down it next to a silver coin. The magnet should slow noticeably as it passes over the silver due to eddy current induction. This is called the "slide test" or "Faraday test" and it specifically catches silver-plated tungsten or lead fakes that pass simple weight checks.

Sigma Metalytics and electronic testers

For purchases above $1,000, an electronic tester is worth the investment. The Sigma Precious Metal Verifier uses electromagnetic resonance to identify the metal beneath any plating, costs about $700, and is conclusive against tungsten cores. Used by major dealers as a final check.

Where counterfeits come from

The vast majority of bullion counterfeits originate in specific Chinese workshops that openly advertise "replica" coins online. These are not deceptive when sold honestly as replicas; they become counterfeits when resold by third parties as genuine. Avoid buying any bullion from auction sites unless the seller is a recognized dealer with a return policy.

Red flags to watch

Be skeptical of: any coin sold "below spot," sealed mint tubes from non-original distributors, "estate find" lots from non-coin-shop sellers, and any coin where the seller refuses to allow weighing before purchase. Legitimate dealers expect verification; counterfeiters resist it.

Bottom line: Counterfeit bullion is a manageable problem if you adopt a four-test routine for every purchase. The total cost of equipment is under $300 and pays for itself the first time you catch a fake.