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<p>[QUOTE="-jeffB, post: 3079543, member: 27832"]I'm still deeply, <i>deeply</i> skeptical of Sigma's claims. I have no doubt they can tell a 90% Franklin or Morgan from a silver-plated steel copy. I'm not as sure they can tell 90% silver from a silver-plated <i>copper</i> core.</p><p><br /></p><p>But if their machines read wrong on Franklin halves, and they're saying "well Franklin halves aren't really 90% silver/10% copper, the Mint cheated on those", it sets off <i>all</i> my alarms. At the VERY least, I'd expect them to borrow an XRF scanner and <i>demonstrate</i> that some Franklin halves are made of the wrong stuff. If I were in their shoes, I'd gather up coins that produce incorrect readings and send them off to a lab for a totally destructive and totally accurate quantitative analysis.</p><p><br /></p><p>Their manual says that the machine can read incorrectly on "deeply embossed" coins. My take is that their machine is a <i>lot</i> more sensitive to SHAPE than to composition -- that worn-flat coins will register as expected, but a well-struck Franklin is likely to fail. (I don't have the math chops to figure out the AC electrical properties of an irregular solid, so I can't prove my claim, but I'm pretty confident in my intuition here.)</p><p><br /></p><p>Blaming it on the Mint using substandard silver? Yeah, I'm going to need to see some independent confirmation. Coin composition is kind of a big deal, and always has been, especially when PMs are involved.[/QUOTE]</p><p><br /></p>
[QUOTE="-jeffB, post: 3079543, member: 27832"]I'm still deeply, [I]deeply[/I] skeptical of Sigma's claims. I have no doubt they can tell a 90% Franklin or Morgan from a silver-plated steel copy. I'm not as sure they can tell 90% silver from a silver-plated [I]copper[/I] core. But if their machines read wrong on Franklin halves, and they're saying "well Franklin halves aren't really 90% silver/10% copper, the Mint cheated on those", it sets off [I]all[/I] my alarms. At the VERY least, I'd expect them to borrow an XRF scanner and [I]demonstrate[/I] that some Franklin halves are made of the wrong stuff. If I were in their shoes, I'd gather up coins that produce incorrect readings and send them off to a lab for a totally destructive and totally accurate quantitative analysis. Their manual says that the machine can read incorrectly on "deeply embossed" coins. My take is that their machine is a [I]lot[/I] more sensitive to SHAPE than to composition -- that worn-flat coins will register as expected, but a well-struck Franklin is likely to fail. (I don't have the math chops to figure out the AC electrical properties of an irregular solid, so I can't prove my claim, but I'm pretty confident in my intuition here.) Blaming it on the Mint using substandard silver? Yeah, I'm going to need to see some independent confirmation. Coin composition is kind of a big deal, and always has been, especially when PMs are involved.[/QUOTE]
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