No Date Visible - Determining 92.5% From 80% Silver George V Coins?

My first reply simply points out that Yes there is a way..if..you really..need to..know.

Otherwise the truth of the matter is..


IMHO

Argh, that app is called CoinTrust and they want $13.99 for it. Nope :P
I love the idea though! They use frequency plots of what sounds the coin makes as it spins/rattles/settles on a hard surface. And compare that to a known frequency response.



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It would be worth trying the tissue paper test; perhaps the 80% silver might appear a little darker behind the tissue. The ring test sounds like a neat idea to try, but I would be afraid that coin geometry might confound the test too much; it is possible that the ring depends more on the level of wear than the composition.

For the magnet test, it's not an issue of para/diamagnetism. Both copper and silver are weakly diamagnetic, and this effect would be exceedingly difficult to test, without a water bath or extremely sensitive scale. What I was thinking is to drop the coin down a chute of sorts so it passes in close proximity to a very large and strong NdFeB magnet. If it is sterling silver, it should slow down more than if it is 80%, since the alloying with copper should decrease electric conductivity and subsequent eddy currents when passing through the magnetic field.

If you have a big magnet and can figure out a timing rig or sensitive way to separate the two based on how the magnet slows the coin, this would be my first go at separating them non-destructively.