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<p>[QUOTE=&quot;KurtS, post: 2252454, member: 11786&quot;]Has anyone ever performed specific gravity tests on their coins?&nbsp; A while ago, I did a slew of tests and found the results very interesting, particularly for silver coins.</p><p><font size="5"><br /></font></p><p><font size="5"><b>Control group tests</b></font></p><p><br /></p><p>The methodology for testing specific gravity is very simple and can be performed accurately using a good jeweler&#039;s scale. To get a baseline of accuracy, I first tested a <i>control group</i> of 9 bronze or cupro-nickel coins where <i>composition </i>probably varies little, given less economic motive for debasing. In the chart below, the darker vertical bar shows the actual specific gravity for each coin, and the lighter top bar indicates any disparity between measured values and specs for each coin. Interestingly, the discrepancy only varies from <b>0-1.6%</b>, which I consider <i>remarkably low</i> considering my <i>&#039;home lab&#039; </i>results against any possible variances in coin alloys. Each value below represents an average of 3 tests on each coin.</p><p><br /></p><p><b>Coins represented by the control sample.</b></p><p>1. US Lincoln bronze cent, average of 3 coins: 1958, 1968, 1972.</p><p>2. Canada bronze cent, average of 3 coins: 1943, 1962, 1965.</p><p>3. Australia 1989 bronze 2 cent</p><p>4. Australia 1943-m bronze halfpenny</p><p>5. Finland 1 Markka (cupro-nickel)</p><p>6. US 2006 CuNi 5c</p><p>7. Iceland Bronze 1956 1 Eyrir--a very small coin, and <i>predictably </i>the greatest discrepancy.</p><p>8. Poland CuNi 1995 1 Zloty</p><p>9. Canada 1940 Ni 5c</p><p><b><br /></b></p><p><b>Graph of control group results:</b></p><p><br /></p><p><img src="https://c1.staticflickr.com/1/736/21549509813_cc5eb62137_b.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><font size="5"><br /></font></p><p><font size="5"><b>Results for testing silver coins</b></font></p><p><br /></p><p>Given the apparently close tolerances of the control group, I was surprised by the greater discrepancy for the silver coins I tested. While some were <i>very close</i> to mint specifications, others were <b>under density by as much as 6.8%</b>, as in the case of one 1943 Newfoundland 10c. This <i>suggests </i>to me the actual silver content was often lower than official mint specifications. If this is due to errors introduced by my methodology, it’s interesting to note that the discrepancies, with one exception, were all on the<i> lower end</i>.</p><p><br /></p><p><b>Test results for sampled silver coins—and corresponding mint specs. Samples were clean, undamaged and relatively free of tarnish.</b></p><p>1. Australia 1916 Shilling, SG test approx. .<b>800</b> silver / .200 copper ; mint spec: .925 silver</p><p>2. Australia 1924 Shilling (this tested <i>slightly higher than sterling</i> .925) mint spec: .925 silver</p><p>3. Australia 1959 Shilling, SG tested <i>below .<b>300</b></i> silver / .700 copper; mint spec: .500 silver</p><p>4. Australia 1921 Sixpence, SG tested ~.<b>750</b> silver / .250 copper; mint spec: .925 silver</p><p>5. Australia 1934 Sixpence, SG tested ~<b>.925</b>; mint spec: .925 silver</p><p>6. Australia 1942 Sixpence, SG test approx.<b> .600</b> silver / .400 copper; mint spec: .925 silver</p><p>7. Australia 1954 Sixpence, SG test approx. <b>.350</b> silver / .650 copper; mint spec: .500 silver</p><p>8. India 1913 1 Rupee, SG tested close to <b>.835</b> silver / .165 copper; mint spec: .917 silver</p><p>9. US Kennedy 50c 1964, SG tested approx. <b>.800</b> silver / .200 copper; mint spec: .900 silver</p><p>10. Switzerland ½ Frank. Two different coins, <i>exact same SG results</i> as <b>.500</b> silver / .500 copper : mint spec: .835 silver</p><p>11. Canada 1947 25c, SG ~ <b>.750</b> silver / .250 copper; mint spec: .800 silver</p><p>12. Canada 1913 10c, SG ~ <b>.700</b> silver / .300 copper; mint spec: .925 silver</p><p>13. Newfoundland 1943 10c, ~ <i><b>.500</b> silver / .500 copper; </i>mint spec: .925 silver!</p><p><br /></p><p><b>Graph of SG results for silver coins. Note: I provided baselines for .500, .800, and .925 silver content.</b></p><p><br /></p><p><img src="https://c2.staticflickr.com/6/5770/22170558355_03a82a737c_b.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><br /></p><p><br /></p><p><b>Finally, a short table of SG values for various Ag/Cu alloys:</b></p><p>.999 = 10.49</p><p>.925 = 10.36</p><p>.900 = 10.31</p><p>.835 = 10.23</p><p>.800 = 10.17</p><p>.750 = 10.08</p><p>.600 = 9.84</p><p>.500 = 9.68</p><p>.400 = 9.53</p><p>.300 = 9.38</p><p>.200 = 9.23[/QUOTE]</p><p><br /></p>

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