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 Replies: 10 / Views: 5,228 |
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Pillar of the Community
United States
814 Posts |
So an 1883-O Morgan that I won on ebay last week came in the mail yesterday. While obviously more harshly cleaned than the seller's pictures alluded to, it weighs only .08g under and is not magnetic. I did a ping test against a 1921 Morgan and a 1925 Peace and while the ping was very close to the two other coins, it was slightly higher. Certainly not like an Ike which pings significantly higher. Aside from the scratches and damage, there is very little actual wear to the coin, so I can't chalk it up to that. I downloaded the Bullion Test app on my phone, and it checks out ok with that. Assuming the coin is authentic, what, then, would cause the slightly higher ping? Edited by hcmusicguy
04/22/2015 12:33 am
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Moderator
 United States
23522 Posts |
There may be a tolerance for ping testing, but I personally have no tolerance for it. With all due respect, what does a half-step on a piano sound like? And why are you striking coins? Is this a fingernail thing?
Honestly, man, no kind of ring test is appropriate for a coin. I would imagine even a patina could change the character of a ring, especially to educated ears like yours (inferring from your nick).
Another professional musician who also happens to be a Morgan collector might have an answer, but if they do I'm going to chide them about striking coins as well.
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Bedrock of the Community
Australia
21786 Posts |
I do a comparative ring tone test by resting both a suspect coin and a genuine known equivalent on the tips of gloved fingers above a soft surface, lest they fall. Gently tap the edge of each, but not hard enough to knock them off your fingers. The coin in question is about 1.0 % below weight. That weight is outside the Weight Tolerance of about 0.4%. That brings the coin into question about it's authenticity, and needs further investigation. The difference in weight to standard may help to explain the difference in ring tone. The difference in ring tone may also be caused by a different alloy. Taking the coin to a bullion dealer had having it XRF tested may help to settle the matter. If the coin IS authentic, the difference in ring tone may? be caused by some small foreign matter inclusion in the metal |
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Pillar of the Community
Sweden
1078 Posts |
I have noticed that sometimes when ringing coins, some make a different, less clear sound. This applies to silver coins. I don't know what causes this but it appears in both modern and older coins. I have noticed most sound change in Copper-nickel coins, many of my US nickels are affected. Maybe your Peace dollar is affected by this? |
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Pillar of the Community
 United States
814 Posts |
sel, According to my calculations (which may or may not be wrong), .08g is not quite 0.3% off, so that would be within Weight Tolerance. |
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Moderator
United States
23522 Posts |
I'm probably just demonstrating intolerance, but it would seem difficult to me to set up a consistent controllable testing regimen. Is the tip of your finger precisely of the same square area every single time? If you're talking half-tones, I'd think a minor variance in the amount of support area under the coin would have relevance.
But I don't do this, so I've no experience to learn from.
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Bedrock of the Community
United States
17884 Posts |
The ring test is not a very good test for authenticity. Too many variables in what goes into producing the sound. Area of surface contact with the support, force of impact of the ringer, exact composition, the pressure of the strike (Creates slight variations in density from coin to coin), any hidden inclusions in the metal of the coin etc. And then you are listening to it with frankly a not very precise instrument, the human ear. The weigh tolerance for a Morgan dollar was +/- .097 grams so it is within tolerance. |
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Moderator
United States
23522 Posts |
Quote:
And then you are listening to it with frankly a not very precise instrument, the human ear. My hearing was pretty good before I ruined it blasting stuff in the woods without hearing protection. Now, with tinnitus, everything's a ring test.  |
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Pillar of the Community
United States
814 Posts |
I showed the coin in question to 2 trusted coin dealers, and both insisted almost immediately that it is legit.
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Pillar of the Community
Canada
5393 Posts |
Maybe the coin is a falsetto or hi soprano  |
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Bedrock of the Community
Australia
21786 Posts |
Many factors can affect a ring tone test:
thickness
diameter
weight
density
different alloy
wear.
In rare cases some of these out of tolerance measurements could cancel each other out to give the same tone.
Best to have both coins pinged at exactly the same time.
A 'beat frequency' can be heard that can be as little as one or two Hertz (cycles per second). They can sound the same if the coins are compared one after the other.
That 'beat frequency' can be enough to arouse suspicion, but not enough to prove authenticity.
That 'beat frequency' should provide sufficient justification for other more serious tests to be carried out.
If the pitch is obviously different then it can be almost, but not quite, concluded that the coin in question is not authentic.
The beauty convenience of a ring tone test is that it costs nothing, and with a bit of handling skill, can be done by anyone. The only piece of equipment that is required is a known genuine coin of the same mint tolerances to test it against.
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Replies: 10 / Views: 5,228 |
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Posted 04/22/2015 12:26 am
