Quote: paralyse, the Sigma Metalyics testers, tests the resistance of the metal /alloys and the the company has compressive data set for different metals and alloys used in coin minting. If you want to learn more, youtube has good videos about it, search for "Signa Metalyics. LOL XRF gold standard, yes I agree and I am a tool gadget guy. However, my wife would divorce me if I spend $20K for a Niton gun.
Learned something new today, I now know what a "Sigma tester" is!
For you gadget guys, I have attached three pictures: first is with the calibration piece, second is a 1923 Pease dollar that tests good, and third is one of the coins in question and as you can see it is way off to high side of the range for this time period.
You'd know your machine batter than us, but my first suggestion would be to take the coins out of the 2x2s - unless you can verify that the 2x2s and the staples are identical in composition and thickness.
Plastic is not an electrical conductor, and a thin layer of plastic might give a falsely high reading of resistivity.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Sap, as promised, I removed the coins from the 2x2's and retested them. Same results. Resistivity=2.31 and greater. With comparing them with 12 period coins that test good, my conclusion is they fail the metal alloy test. Not sure what that means, as the consensus here is that they are good coin (mint struck).
Well then, it sounds like something is indeed afoot.
Increased resistivity implies either something coated onto a normal coin, or that the coin is not made of as pure a silver as it should be. Low silver quality should not be happening in 1924. Which in turn implies it's a high-quality counterfeit.
Next step, I would suggest trying to find an XRF tester you can double-check it with. Jewellers and "we buy gold" scrap metal merchants often have one that's specificlaly calibrated for precious metals. If the XRF comes up with 90% silver, then there's something odd happening with your tester (or an invisible layer of something highly resistive but transparent to X-rays is sitting on the coin). A low silver reading by XRF would confirm the counterfeit hypothesis.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Another test is to find an App for your phone that determines the resonant frequency when the coin is "pinged" on a hard surface. I have "ping coin" and I am sure that there are others.
Oriole, this was the firt time I used the ping test. I used 2 different apps and I rang each coin multiple times most of the pings are good and some failed on each coin. I do not have any experience with the ping test so not sure how to interpret these results? Good, maybe, inconclusive?
I think we are beating a dead horse at this time until I get some XRF date.
I have always been wary of using "the ping test" for identifying authenticity and/or metal composiiton of a coin. The sound a metal object like a coin makes when it rings depends as much on shape and internal structure as on composition. So a heavily worn coin should "sound" different from a mint-state coin, and if there's any planchet flaws that will also change the sound.
In other words, while a "matching ping" can be take as confirmation of authenticity, a "wrong ping" is not necessarily an indicator of a bogus coin.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Sap I agree, the ping test is another data point in the puzzle and we have to look at the whole picture. I will keep on working on it and if I get additional data it will be shared here. Thank you all for the great input and discussion. Cheers, SJ
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Posted 03/11/2023 6:49 pm
