I have a 1999 Philadelphia mint Delaware quarter. The quarter has the mint error spitting horse. It has also been confirmed that it has been struck on a silver planchet that is 90% silver. And the weight is 5.70 grams. HOW CAN THIS BE?
Can you elaborate on this? Because if it looks silver (solid silver edge, looks light rather than dark when viewed through paper), but weighs 5.7 grams (normal clad weight plus ~30 milligrams), it's probably silver-plated. There are lots of state quarters that got plated with gold, silver, or platinum. Welcome to CoinTalk!
Yes I know it's light for silver, but it has been placed on the sigma verifier that it is 90% silver. I too thought that it might have been silver plated. I was also informed that the silver coins were minted in San Francisco.
I absolutely would not trust a Sigma to distinguish between a 90% silver coin and a clad coin plated with .999 silver. Given the skin effect, and given that .999 silver is likely more conductive than 90% silver, I would expect the tool would see the two as nearly identical. I trust the scale a lot more than I'd trust the Sigma.
I've had to coin shops tell me that it is 90% silver and that it could have been a planchet that wasn't even supposed to be used for the quarter series. What's your thoughts.
I was not looking to sell the coin but rather gather information about the validity of the coin. Both dealers were very interested in the coin and in fat called other coin professionals. I still would like to know if there is a possibility that an underweight silver planchet could have gotten into the Philadelphia mint
If the dimensions are correct (i.e. thickness, diameter) and it weighs 5.7 grams, it is not silver... the edge may just be smeared covering the copper.
Thanks everyone for your posts. Other than its weight is there another way to tell if it's solid silver?
You can do the specific gravity test, but you will just waste your time... if it fails the weight/dimensions standards, it is not silver.
Okay I get that it's under weight my next question would be can anybody tell me whether a sigma precious metal verifier can tell whether a coin is solid silver or not
The "dimensions" part is important. If it's a foreign or underweight silver planchet, it should be thinner than expected, and the design should be at least a little weak (although that may not happen if the difference in thickness is small). But for this explanation to fly, we need a foreign silver planchet that weighs 5.7 grams. Is there any such thing? It's a lot easier to believe that this is a clad quarter (very common), plated with silver (also very commonly done). I'm sure the Sigma folks will swear that their machine wouldn't be fooled, but I'm not convinced.
Because how many would they sell if they didn't say that? If all they're sending through the coin is electromagnetic waves, I want to see how they can "read past" a silver coating to distinguish silver-coated copper from solid silver. I can imagine techniques that might let them do it, but I seriously doubt that they can distill that down into a reliable "yes/no" (or, given what I've seen about the machine, a 0-100 readout with a guide that says "any reading in this range is solid silver"). But, again, I don't have the machine and test pieces in hand, so I could be wrong. Note that the thread I linked describes the machine getting confused about gold composition. Maybe the US mint silently changed the composition of commemorative half-eagles, making each contain more gold than advertised -- but I think the more likely explanation is "the Sigma isn't perfect".
