I thought from reading someplace that the Sigma used ultrasonic waves , and the transducer sure looked like a probe I have seen in a disassembled medical ultrasound hand piece, and might explain why it has a larger version for more bulky samples? Hasn't someone mentioned using one? Ok here are a couple of threads,, https://www.cointalk.com/threads/sigma-metalytics-modern-5-half-eagles.296929/#post-2749006 https://www.cointalk.com/threads/sigma-precious-metals-verifier.249230/#post-1953669
http://www.sigmametalytics.com/information.html I'll admit that I'm thinking mostly about induced current and back EMF, not direct B-field (magnetic) effects, but I think Sigma's claims are -- well, strongly optimistic. I'd love to see an experiment showing that I'm right or wrong!
Thank you desartgem the video that you posted definitely illustrates that the device will read through plating. That being said I feel that I have a silver planchet that is underweight at 5.70 grams. I guess the next question would be how could this planchet get into the Philadelphia mint and be struck in production? Does anybody have any thoughts?
If the dimensions are correct and the weight is 5.7 gms, it CANNOT be an under weight silver planchet, unless it has a large internal void. In order for a round silver planchet to be underweight, it would have to rolled thinner. These occurrences are pretty unlikely but possible, as the are known thin planchet errors. And, the mis-rolled strip would have to be at a thickness which just happend to yield a planchet weight close to a clad planchet. Then that planchet would have to get stuck in some equipment or tote at the SF mint. Finally, that tote or equipment would have to get shipped to the Philly mint, the planchet would have to become dislodged at some point before striking, make it to the dies. Or it could be plated. To paraphrase William of Ockham, the simplest answer is usually correct. Or you could drop approx $30, and send it to a TPG that specializes in errors for authentication
I have about 20 ROLLS of statehood quarters that look and weigh exactly as the OP's coin does. All different states too. What are the chances that even one of mine is an underweight silver planchet that somehow got smuggled into the Philly mint and then ....what? How many of these exact plated quarters have we see right here on Cointalk?
Thanks for everyone's replies. There is a coin show in Grapevine Texas that I will take it to and see what some of their experts think. It may just need to go to PCGS to be authenticated
Be careful in the face of a sales pitch. The video showed the device reading SILVER through GOLD plating. That's a very different challenge; silver is highly conductive and not at all magnetic, and gold plating is far too thin to interfere with the resulting signal. The video also showed the device identifying .999 silver, but rejecting .999 silver plated over -- well, he doesn't say what the interior of the coin is. If it was steel or another magnetic material, I'm quite sure their $700 machine could distinguish it from silver. Of course, so could a 10-cent magnet. What the video did not show is the machine distinguishing between pure silver and silver-plated copper. The electrical differences between copper and silver are very small -- the conductivity difference is around 5%, and the permittivity/susceptibility difference is a couple hundredths of a percent. It's possible that Sigma is able to pick this difference up, but I'm not convinced, and the video does nothing to convince me. Like @Oldhoopster says, for this to be an actual underweight 90% silver planchet, you need a whole stack of unlikely coincidences. For it to be a silver-plated clad quarter, misread by a machine, all you need is a common plated coin, and physics.
That's an excellent plan. Please follow up here. If it's an actual silver planchet, we'll all be interested to hear that, and we'll have some work to do figuring out where it came from. If it isn't, and the Sigma has this large and critical of a blind spot -- well, that's important too!
The show is not till the end of this week I will reply later to let you know what their thoughts are. Again thank you everyone for your comments on cointalk.com
No. There could be a slight chance that a rejected 90% silver proof planchet might be able to get to the Denver mint, but not Philadelphia. And 5.7 grams would be SERIOUSLY underweight. Can't be a foreign planchet because the mint stopped striking foreign coins in 1984. Not likely to be a foreign planchet mixed in with blanks coming in from an outside contractor because the only blanks coming in were cent blanks. It is REALLY unlikely you would have a silver planchet that much underweight, but if you really want to try and confirm it a specific gravity test should be your next step. Ricko mentioned the dimensions but there is no real way to check the thickness dimensions of a struck coin, so SG is the best option. My vote is on silver plated.
Okay guys I said that I would get back with you after I found more information about the spitting horse made out of silver. One of our conversations was concerning the sigma metalytics machine. Although it was reading 90% silver I contacted Sigma and they told me that it could be a false positive that copper and silver were really close in conductivity. After speaking with Sigma they informed me that if we put the machine in measurement mode it will give us some conductivity readings in this mode they can tell whether a coin is silver or just a conventional quarter. It still does not tell the composition of a coin to do this I took the coin to someone that had an xrf verifier. That machine confirm that it was not silver but plated with Platinum. Now the next question. I refered to my coin as the spitting horse. So what would the worth be of a spitting horse that is plated with Platinum? Any thoughts.
Show the whole coin with the mint mark. They made silver proofs in San Fran. But I doubt this is a proof, and the odds of a silver planchet in Philly or Denver ending up as this coin is almost zero.
I'll prepare to repeat this here whenever the subject comes up, because you can be sure you won't be seeing it in Sigma's promotional material. Sigma CANNOT reliably distinguish solid silver from copper with silver or platinum plating. At least not in the standard "go/no go" mode. Thanks for following up!
If the Sigma says it is silver, it is most likely either plated or silver vermeil. Vermeil is a nice word for gilding over some other metal, in this case a cupronickel obverse and reverse clad to a copper center. To test if it is silver vermeil (ver may) or plating, try a good vigorous rub with an abrasive polishing cloth which will remove either to reveal the cupronickel under it. Do a small area on the rim and test with Sigma again. You could also drop test it on a nice hard surface with another 90% silver coin. I'm sure you'll hear the difference. Without seeing it in hand and looking at it all over, it appears to have been gilded more than plated. There are still some crazy folks that do gilding even without a respirator plumbed to medical oxygen. They generally don't live long.
