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 Replies: 10 / Views: 1,524 |
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Pillar of the Community
United States
1137 Posts |
I can not think of a thing in the minting process that would cause these lines, these have to be some kind of PMD but they look like that are part of the metal itself, not on the metal, also, why would the lines not be on the rim of the coin? Any insight for this would be appreciated.    |
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Moderator
 United States
56855 Posts |
It is called a woody.woodgrain Resulted from impurities in the alloy or concentrations of pure copper that did not properly blend with the 5% tin and zinc added to it. When these less than perfect ingots were rolled into strip, from which blanks would later be punched, the concentrations were flattened and stretched into the patterns seen on the finished coins. Invisible when first struck, these flaws appeared only after the coin was exposed to atmospheric agents that caused the copper concentrations to tone more quickly than the properly mixed portions of the planchet. John1  |
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Moderator
United States
23522 Posts |
Can you say, "definitive?" I thought you could.  |
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Pillar of the Community
 United States
1137 Posts |
John1, that is very interesting and I thank you for the detailed explanation. Why does the rim appear unaffected, is it because of more wear on that part of the coin?
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Moderator
United States
23522 Posts |
Quote:
Why does the rim appear unaffected, is it because of more wear on that part of the coin? The rim has been through the upsetting mill in its' creation; metal has been physically rearranged and rearranged a second time during the strike, in the collar. The fields and devices are far closer to their original configuration, as-rolled in the original planchet strip. |
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Pillar of the Community
United States
1137 Posts |
You folks are great! Thank you!
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Bedrock of the Community
Australia
21786 Posts |
John1 & SsuperDdave: Ta for the info.
I knew a little on this subject, but now I know a lot more.
One of the reasons the CCF exists!
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Pillar of the Community
United States
1234 Posts |
 gotta love this place  |
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Pillar of the Community
United States
2624 Posts |
I think these are striations. Is the surface smooth or "rippled"?
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Pillar of the Community
United States
1137 Posts |
Surface appears to be smooth at 80x magnification, there is no light reflection coming off of those lines.
Edited by chzman
01/05/2014 12:46 am
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Moderator
United States
56855 Posts |
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John1, that is very interesting and I thank you for the detailed explanation. CCF's glossary can be your friend too John1 |
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Replies: 10 / Views: 1,524 |
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Posted 01/04/2014 5:30 pm
