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<p>[QUOTE=&quot;Pickin and Grinin, post: 2791726, member: 73995&quot;]<a href="http://coinauctionshelp.com/mintingprocesshistory.html#.WWD8B4jyvIU" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://coinauctionshelp.com/mintingprocesshistory.html#.WWD8B4jyvIU" rel="nofollow">http://coinauctionshelp.com/mintingprocesshistory.html#.WWD8B4jyvIU</a></p><p><br /></p><p><b>Mint Marks</b></p><p>Mint Marks began being added to U.S. coins starting in 1838. Continuing to this day The Department of Engraving &amp; Design&#039;s Die Manufacturing Division located within the Philadelphia Mint has produced nearly all Engravings/Galvanos, Master Hubs, Working Hubs, Master Dies and Working Dies used to produce all U.S coins (In 1996 the Denver Mint also began acting as an auxiliary die production facility when demand requires). Until the mid 1980&#039;s all working dies produced at the Philadelphia Mint had the Mint Mark hand punched into each one individually and sent to the various other Mint Branches for distribution with whatever the destination mint&#039;s MM letter was. </p><p>Sometimes impressing the MM into the working dies required multiple strikes and if there was movement or misalignment in between strikes a RPM could be created and passed on from the Working Die to all coins it was struck by.&nbsp; Beginning around 1965 the Mint Marks were hand punched into the Working Hubs instead of the Working Dies which cut down on the number of RPMs but they were still possible.</p><p>Beginning in 1985/86 for Proof Coins and the early 90s for normal Business Strikes the Mint Marks we no longer stamped into the working dies by hand rather engraved directly into the original design/plaster mold for all denominations. Due to this RPMs are not found on coins after about 1991.</p><p><br /></p><p><br /></p><p><br /></p><p>The last paragraph here stated why coins after 1990 DO NOT have RPM&#039;S.</p><p>The Master die is not a hardened steel, requiring a major amount of force to implement a MM. It is made of a much softer composition, therefore no need to strike it twice, if it was even struck. The mm was probably added by machine.</p><p><br /></p><p>The only MM that I know of after 1990, that is truly doubled is the 1995 D.</p><p>But, this is a DDO, not an RPM. IMO for an RPM to ever show up and be attributed after 1990. The single squeeze process would have to be the culprit.</p><p>This would be very difficult because no other device on the coin could show rotation, except the MM. Then and only then would it / or could it, get the attribution.&nbsp; The experts still may call it a DDO, not a RPM.[/QUOTE]</p><p><br /></p>

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