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<p>[QUOTE=&quot;GDJMSP, post: 1019423, member: 112&quot;]Mike from what I have found in my research zinc plates are what was used to polish dies even before the US Mint opened. And while I cannot say definitively that they are still being used even today, I can say that they were still being used up until not too dang long ago.</p><p><br /></p><p>As for why the lines appear to be straight, that&#039;s common sense. Take an object an 1 1/2 inches in diameter or smaller and place it against another object 10 or 12 inches in diameter. The interface between the two will appear to be a straight line to the human eye, even though it is a very shallow arc.[/QUOTE]</p><p><br /></p>

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