Coin Reference

This page is a reference for bars and coins that are either known to be good but give odd readings or known to be frequently counterfeited.

Click on the name of the bar or coin you're interested in to see our information on it.

The best way to catch any counterfeit is to check all aspects of a sample, including the resistivity as measured by a Precious Metal Verifier, the thickness, diameter, weight, markings, and finish. All aspects of a genuine sample will be within a very small tolerance range, if not exactly the same as the published specifications.

If you have questions or concerns about a specific sample, please give us a call at (530) 562-4589 or email us at info@sigmametalytics.com

Gold

There are a number of genuine 1978 - 1982 gold Panda coins which read outside of the range on the PMV Original, PRO, PRO Mini, and Investor despite being authentic pieces. We believe these coins have higher than usual iron contaminants, but are still .999 gold. The iron content pushes their resistivity readings to the right out of the range.If your coin is the correct size and weight, has the correct markings, and is not magnetic, then it is likely genuine if it reads near the acceptable resistivity range.
In June 2021, Sigma Metalytics found a counterfeit 2013 gold Krugerrand which read within the brackets on the PMV Original. The counterfeit was found to be close in size and weight, but not exactly correct. We recommend checking your 2013 Gold Krugerrands to ensure they are the correct size and weight using the below specifications. Year: 2013 Type: Krugerrand Alloy: 91.67% Gold, 8.33% Copper Weight: 33.93 grams, with ± .05 grams acceptable variance Thickness Measured by Calipers from the Rim: 2.84mm Diameter Measured by Calipers: 32.8mm Please call or email us if you have any question about your 2013 Krugerrand.
There are a number of genuine 2018 gold Eagle coins which read outside of the range on the PMV Original, PRO, PRO Mini, and Investor despite being authentic pieces. We believe these coins have higher than usual iron contaminants, but are otherwise still 91.67% gold, 3% silver, balance copper. The iron content pushes their resistivity readings to the right out of the range. If your coin is the correct size and weight, has the correct markings, and is not magnetic, then it is likely genuine if it reads near the acceptable resistivity range.
There are a number of genuine 2018 gold Libertad coins which read outside of the range on the PMV Original, PRO, PRO Mini, and Investor despite being authentic pieces. We believe these coins have higher than usual iron content, but are still .999 gold. The iron content pushes their resistivity readings to the right out of the range. If your coin is the correct size and weight, has the correct markings, and is not magnetic, then it is likely genuine if it reads near the acceptable resistivity range.
There are a number of genuine 2024 gold Libertad coins which read outside of the range on the PMV Original, PRO, and Investor, despite being authentic pieces. We believe these coins have higher than usual iron content, but are still .999 gold. The iron content pushes their resistivity readings to the right out of the range. The 2024 Libertads we have seen read outside of the range have had a resistivity around 3.0-3.1. If your 2024 Libertad has a resistivity higher than 3.1, that is a highly questionable sample. If your coin is the correct size and weight, has the correct markings, and is not magnetic, then it is likely genuine if it reads near the acceptable resistivity range.
Many of the genuine OPM gold coins and bars sometimes read outside of the range on the PMV Original, PRO, PRO Mini, and Investor despite being authentic pieces. We believe these coins and bars have higher than usual iron content, but are still .999 gold. The iron content pushes their resistivity readings to the right out of the range. If your bar or coin is the correct size and weight, has the correct markings, and is not magnetic, then it is likely genuine if it reads near the acceptable resistivity range.

Silver

We have seen a number of 1921, 1923, and 1928 silver dollars (sometimes called Morgan Silver Dollars, sometimes called Walking Liberty Silver Dollars) fail the resistivity test on the correct 90% silver 1900-1945 setting. We believe the US Mint used old silver from the late 1800s in these coins without first cleaning the silver of contaminants. Because of this, they test outside of the acceptable range on the 1900-1945 setting. We recommend testing these samples on the pre-1900 setting. All genuine 1921, 1923, and 1928 silver dollars should pass the resistivity test on the pre-1900 setting. If the sample still does not pass on the pre-1900 setting, it is highly questionable. Generally, the US Mint was somewhat relaxed with its contaminant standards for silver in the early and mid 1900s. If your sample is falling just outside of the expected range, try testing it on one era prior to its expected era (e.g., test a 1948 silver coin on the 1900-1945). If it passes, it is most likely genuine, but with some higher than usual contaminants. If it still fails, it is a highly questionable sample. Regardless of the resistivity result, the sample should always be tested for size and weight to ensure it has the correct specific gravity for the alloy and sample type.
On our PRO devices, the "Pure Silver" range is calibrated to put 99.99% silver samples in the green range and 99.9% silver in the yellow on the right. We calibrate the devices this way due to the number of counterfeit 99.9% coins in circulation. The yellow range is a caution sign to remind users to check the other aspects of their sample (dimensions, weight, and markings). If your bar or coin is the correct size and weight, has the correct markings, is not magnetic, and reads within the yellow or green range, then it is likely genuine.
We occasionally see older Engelhard silver bars read outside of the expected range despite being genuine. These bars either have higher than usual contaminants or are around .995 silver rather than .999. If your bar or coin is the correct size and weight, has the correct markings, and is not magnetic, then it is likely genuine if it reads near the acceptable resistivity range.
Modern sandwich quarters will read within the acceptable range on PMV Originals and PROs on the 90% Silver Balance Copper setting. Modern coinage is designed to have the same resistivity to ensure they work in coin machines with older coinage. The best way to ensure your quarters are 90% silver is to check their weight. Below are the specifications for both modern and pre-1965 quarters. Year: Pre-1965 Type: U.S. Quarter Alloy: 90% Silver, 10% Copper Weight: 6.25 grams Diameter Measured by Calipers: 24.3mm | Year: Post-1965 Type: U.S. Quarter Alloy: 91.67% Copper, 8.33% Nickel Weight: 5.67 Grams Diameter Measured by Calipers: 24.3mm