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<p>[QUOTE=&quot;Oldhoopster, post: 3637540, member: 84179&quot;]I would be hesitant to use a Sigma on ancient coins.&nbsp; The resistivity measurement is influenced by the alloying metal as well as the internal structure (voids, porosity, incomplete alloying, etc).&nbsp; You can ignore these variables for modern coins as the process for making the blanks is uniform.&nbsp; But for ancients...?&nbsp; Cast blanks with who knows what else is in the mix.&nbsp; Not something for an accurate resistivity measurement.</p><p><br /></p><p>Not sure if you&#039;re still in school or finally working in the aerospace industry.&nbsp; If I had easy access to an SEM, I&#039;d get a couple of EDS spectra of the surface and some areas that are cracked.&nbsp; MAYBE you could pick up some differences that would indicate a base metal core.[/QUOTE]</p><p><br /></p>

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