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<p>[QUOTE=&quot;Pickin and Grinin, post: 2635057, member: 73995&quot;]Some thing I found on Wexlers site</p><p><i><b><i>Rockwell Hardness Test Marks</i></b></i></p><p><i><b><i>On Lincoln Cents</i></b></i></p><p><i><br /></i></p><p><i><b>By Pete Apple</b></i></p><p><i><br /></i></p><p><i>The correct degree of hardness is a critical factor in the minting of coins. If an unstruck planchet is too hard the image pressed on the coin will not be clear. If it’s too soft, the coin will wear too quickly. The U S Mint uses a Rockwell Hardness Test on all raw coin material (including copper- plated zinc blanks). (US Mint, E-mail 8/24/2015, Diamond, 2006, Page 16).</i></p><p><i><br /></i></p><p><i>The test procedure involves pressing a 1/16” metal ball into the coin material with a known amount of pressure and measuring the depth of penetration. There are other Rockwell Scale Protocols for harder materials where either a different sized ball or a spheroconical diamond is used to make the indentation. The Scale Protocol currently used for coin material involves the lightest pressure that can be used by a Rockwell tester.</i></p><p><i><br /></i></p><p><i>This same source shows an image (shown beloSw with permission) of an alleged Rockwell Test Mark in planchet on a 1971- Lincoln Cent.</i></p><p><i><br /></i></p><p><i><img src="http://conecaonline.org//images/2016RockwellImages/Figure1.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" />Figure 1</i></p><p><i><br /></i></p><p><i>Read the full story<a href="http://conecaonline.org/content/RockwellHardnessTest.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://conecaonline.org/content/RockwellHardnessTest.html" rel="nofollow">HERE</a></i></p><p><i></i>[/QUOTE]</p><p><br /></p>

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