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<p>[QUOTE=&quot;TheFinn, post: 2907806, member: 90102&quot;]The reason is that the surface of a new coin is not virgin copper.&nbsp; There is a great deal of oil on the surface of new coins. Mints are factories stamping out tools on mechanical presses. And these presses and their tooling is lubricated and covered in thin films of oil to guard against rust. That gets on these shiny new coins. If you don&#039;t believe that, do a residual solvent test after rinsing some new coins in acetone and measure the weight after evaporating the solvent. I worked in a mint, and they are filthy. It&#039;s amazing such shiny stuff comes out. But this thin layer of protects the coins&#039; surfaces against oxidation. As soon as you take it off tarnish will begin to show. That&#039;s why the TPGs don&#039;t guarantee copper - they dip the coins in solvent (acetone) before encapsulation to remove anything that may enhance the grade. They just started the time clock, and the results are a crap shoot.[/QUOTE]</p><p><br /></p>

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