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<p>[QUOTE="Gallienus, post: 2886313, member: 42034"]I was perusing a thread regarding the silver debasement in other coins when I saw a link discussing specific gravity tests on US coinage. </p><p><br /></p><p>According to the tester, some US coins show from his specific gravity tests to be less than 90% silver. Specifically he reported 82.5% silver for a 1964-P Kennedy half and 82% silver for a 2014-D commemorative Kennedy silver half. Both coins are supposed to be 90% silver.</p><p><br /></p><p>The link is here:</p><p><a href="http://www.biblical-data.org/GSDykes_specific_gravity_tests.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.biblical-data.org/GSDykes_specific_gravity_tests.pdf" rel="nofollow">http://www.biblical-data.org/GSDykes_specific_gravity_tests.pdf</a></p><p><br /></p><p>The usual caveats: I've done weighing of coins but never s.g. Even for simple weighing I've found it necessary to buy a Ohaus Analytical scale. The usual $99 digital jewelers' scales are simply not accurate. They will show a small coin as being lighter and a heavy coin as weighing more than they should. Thus it's not just calibrating to a single value to get the correct weight. I have an ASTM weight set for calibration. </p><p><br /></p><p>Even a small weighing error will throw the s.g. off by a large % and I can't find any evidence of scientific method in this paper.</p><p><br /></p><p>Nonetheless if true this is disconcerting. I wonder if anyone else has tested coinage via s.g. or other methods? Of course the type I trimes are 75% silver I think and pre 1837? silver is ~89.26. A google search is fruitless as nobody is concerned with the purity of earlier silver coins in South Florida these days...[/QUOTE]</p><p><br /></p>
[QUOTE="Gallienus, post: 2886313, member: 42034"]I was perusing a thread regarding the silver debasement in other coins when I saw a link discussing specific gravity tests on US coinage. According to the tester, some US coins show from his specific gravity tests to be less than 90% silver. Specifically he reported 82.5% silver for a 1964-P Kennedy half and 82% silver for a 2014-D commemorative Kennedy silver half. Both coins are supposed to be 90% silver. The link is here: [url]http://www.biblical-data.org/GSDykes_specific_gravity_tests.pdf[/url] The usual caveats: I've done weighing of coins but never s.g. Even for simple weighing I've found it necessary to buy a Ohaus Analytical scale. The usual $99 digital jewelers' scales are simply not accurate. They will show a small coin as being lighter and a heavy coin as weighing more than they should. Thus it's not just calibrating to a single value to get the correct weight. I have an ASTM weight set for calibration. Even a small weighing error will throw the s.g. off by a large % and I can't find any evidence of scientific method in this paper. Nonetheless if true this is disconcerting. I wonder if anyone else has tested coinage via s.g. or other methods? Of course the type I trimes are 75% silver I think and pre 1837? silver is ~89.26. A google search is fruitless as nobody is concerned with the purity of earlier silver coins in South Florida these days...[/QUOTE]
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