Muito interessante a informação do primeiro link que partilhou amigo Sílvio. Vale a pena deixar cá este trecho para não se perder:
"silver coins were fairly easy to spot with the naked eye by anyone with even a little experience in the coin market – these leaked photos appear to confirm rumors that have been circulating the industry over the past year – that high quality Chinese counterfeit silver coins are now appearing, duping even experienced professionals when not properly examining and testing coins prior to purchase.
Fake silver coins are becoming a problem in the market, and you can expect the scope of these Chinese counterfeiting rings to only grow as their technology improves and silver prices rise as the bull market accelerates.
How Can the Average Silver Investor Protect Himself From Fake Silver Coins?
Know Where Your Coin Dealer Sources Their Silver Coins.
At SD Bullion, We Source Over 99% of Our Silver Coins Directly From the World’s Leading Mint’s Refineries, and Authorized Purchasers. We’ve Never Purchased an Ounce of Anything From ANYONE in China Outside of Official Gold and Silver Panda Coins from the Chinese Mint. Every Single Coin or Bar Purchased From the Secondary Market (inventory purchased from customers, etc) is Tested for Purity, and is Rejected if the Coin/Bar Fails to Meet Labeled Weight or Purity.
Make Sure Your Coin Dealer TESTS Their Coins, and Know HOW They Are Testing Their Coins.
Ping Tests and Water Density Tests Are Typically Not Accurate Enough to be Relied Upon.
Among Other Purity Tests, SD Bullion Uses the Sigma Metalytics Gold and Silver Purity Testing Scanner to Verify the Resistivity of the Metal.
Even small differences in alloying—for example crown gold (91.67% gold balance copper) and 90% gold (90%gold balance copper) are different. Can the wrong metal or alloy give a Resistivity that looks right?
It is almost impossible to duplicate another coin’s resistivity, weight, and size. For example, silver is the most conductive metal known, so it is virtually impossible to duplicate. Gold is the third most conductive metal (only copper is between them). Platinum and Palladium have almost identical conductivities but are easy to distinguish in other ways.In principle it would be possible for an alloy to be developed that would mimic, for example, American Gold Eagles. But combined with the appearance and weight of the coin, the fake would be obvious. A coin that has about the right weight (for example using tungsten to fake gold) would have a totally different resistivity than gold. Among Other Tests, Using Resistivity One Verify the Purity and Distinguish Between:
Gold – Pure
Gold – 91.7% 22K Crown
Gold – 90%
Gold – American Eagle
Gold – 98.6%
Silver – 99.99% Pure
Silver – 99.9% Pure
Silver – 92.5% Sterling
Silver – Morgan Dollar
Silver – Peace Dollar
Silver – 90% Coin
Silver – 96% Britannia
For larger investors, a Resistivity Scanner Such as the Sigma Metalytics Gold & Silver Purity Scanner Can Provide Added Peace of Mind That Their Investment is Real and Authentic."
O segundo link que deixou explica bem as superfakes, que às vezes quase parecem mais perfeitas que as originais. Qualquer dia a mecânica "arde" toda. Safa-se a manual, que com este método não vão lá.