Patent: magnetic slide could spot fake silver and gold

A magnetic slide that could help untrained investors distinguish genuine gold or silver investment coins and bars from counterfeits – without damaging them – has been awarded a US patent.

The patent (No. 10,497,198) covers a method that uses size and weight of the coin alongside the terminal sliding velocity of a coin or bar placed on the magnetic slide to identify fake gold and silver items “even if a counterfeiter were to alter even a fraction of the precious metal content in a coin by substituting it for non-precious metals or by the use of inserts, laminates, or voids.”

Current techniques to test for pure gold, for example, require the item to be scratched and tested using an acid solution. Magnets are also suggested as one way to tell, as pure gold isn’t magnetic. However, this only works if the substituted metal is magnetic, and there many metals that are non-magnetic and can be plated with gold.

The slide technique has been tested using 22-carat US American Eagle coins and Krugerrands and could be used by investors to check their holdings are genuine, and also as a screening tool, says the patent, which has been awarded to Douglas Arthur Pinnow of Lake Elsinore, California.

It involves testing how quickly the item slows down in the slide, and cross-referencing that with a genuine coin or bar of the same size and weight.

“The current reality is that there is no method or equipment available that can provide holders of pure gold and/or silver coins and bars with 100 per cent certainty that they are not holding some counterfeit coins and bars, without employing tests damaging to the appearance of their coins and bars or that require a technician to perform validation testing using expensive equipment,” it says.

The abstract of the patent appears below:

Method and apparatus for discriminating gold and silver coins and bars from counterfeit

Abstract: Throughout the world, there is growing trend by investors to protect wealth by holding silver and gold coins and bars. Unfortunately, there are also a growing number of counterfeit coins and bars coming into in circulation. This situation cries out for an affordable method that can be used by untrained investors to quickly and reliably discriminate authentic coins and bars from counterfeit ones without causing damage to their coins and bars. The disclosed method fills this need by the use of a combination of conventional and novel designed pieces of equipment for measuring the following three characteristics of a coin; (1) size, (2) weight, and (3) relative terminal velocity on a magnetic slide. The results of these measurements can be used to unambiguously discriminate pure silver and pure gold investment coins and bars from counterfeit ones and can also be helpful in evaluating 22-karat gold coins and pure platinum coins.

US Patent No. 10,497,198