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<p>[QUOTE=&quot;Clawcoins, post: 3362094, member: 77814&quot;]from another thread, I thought I would split this out for it&#039;s not buried in another thread.&nbsp; Just in case other folks are interested in it.</p><p><br /></p><p><br /></p><p>The US MINT has a few Alternative Metal testing documents which includes a few (many) things they did to the dies to increase longevity, etc over time.&nbsp; From die lifes of 300,000 to 1,000,000 with various coatings (to just expecting low quality) including chrome nitride PVD-coated circulating dies which did not increase longevity.</p><p><br /></p><p>There&#039;s so much in these documents, the link below is 400 pages, so I can&#039;t even write a brief about it.</p><p><br /></p><p>They reference Burnishing in there as only the Dollar coin is burnished now as of 2012.</p><p>Costs, metal tests and options for Cents including CPZ - Copper Plated Zincs which uses an 8 micron thick copper plating (now you can post that to all the damaged CPZ pictures you see).</p><p><br /></p><p>400 pages of fun information for the Numismatic Geek</p><p><a href="https://www.usmint.gov/wordpress/wp-content/uploads/2016/06/ctcr-alternative-metals-study-2012-08-31.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.usmint.gov/wordpress/wp-content/uploads/2016/06/ctcr-alternative-metals-study-2012-08-31.pdf" rel="nofollow">https://www.usmint.gov/wordpress/wp-content/uploads/2016/06/ctcr-alternative-metals-study-2012-08-31.pdf</a></p><p><br /></p><p>I&#039;ll try to find the one that is even earlier than this one.</p><p>I have downloaded versions if it doesn&#039;t load.&nbsp; Their servers are slow.</p><p><br /></p><p>just searching for burnish... here&#039;s one hit</p><p>[ATTACH=full]891192[/ATTACH]</p><p>which was done to an A190 strip to improve the metal planchets themselves, and not necessarily the die.&nbsp; As stuff added to the die wears out quickly, whereas to the planchets will keep &quot;lubricating&quot; it, which they picked up from the RCM test samples sent to them for some test.</p><p><br /></p><p>Of course, then they figured out some other process which made burnishing not needed.</p><p><br /></p><p>have fun reading ....</p><p><br /></p><p>oh, they don&#039;t mention half dollars much as they are the same type of composition as dimes and quarters.</p><p><br /></p><p>can someone find a prototype $1,000 coin ... hehehe .. go searching.[/QUOTE]</p><p><br /></p>

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