| Author |
 Replies: 21 / Views: 1,037 |
Page 2 of 2
|
|
|
|
Bedrock of the Community
United States
94367 Posts |
Very interesting as always!
|
|
Pillar of the Community
 United States
6116 Posts |
Interesting article for sure. But while they started talking about proofs, I'm not sure the rest of the article is about proof planchets specifically. Or does SF only make proof coins these days?
|
|
Pillar of the Community
United States
2735 Posts |
Interesting and nice capture of that surface texture.
|
|
Pillar of the Community
United States
2775 Posts |
TB,  The mint's description. Thanks, Doug. Quote:
Special proof and uncirculated planchets go through a cleaning process called burnishing. They are placed in a drum with cleaning agents and small metal pellets to smooth and polish the surface. An employee then rinses the planchets and hand-dries them with towels. https://www.usmint.gov/learn/produc...n-production |
|
Moderator
 United States
96857 Posts |
|
|
Moderator
United States
15466 Posts |
Interesting thread - hope we can come to some sort of consensus.
Take a look at my other hobby ... http://www.jk-dk.art |
|
Pillar of the Community
United States
2775 Posts |
Started not to bring this up as the link below makes reference to Burnishing misconceptions and or post strike burnishing. That is considered PMD. The blank in question here seems to be missing the upset process as well as being UN-struck. After chewing on my thoughts a bit, got me to thinking, is it possible the blank itself was burnished or altered after it left the mint? Still haven't found an example to compare it to. Does the clip edge look typical or pitted like the close up? Thanks, Doug. https://mikebyers.com/coinworld061801.html |
|
Pillar of the Community
United States
6116 Posts |
A little hard to tell but my opinion is that the satin surface does cover the edge of the clip as well as the regular edge. So seems it came to be on there after it was punched and clipped.
|
|
Moderator
United States
96857 Posts |
One would think that any burnishing would be done to a blank (or planchet) after it was blanked from the raw material. I can't see the metal processers burnishing a full 1000 pound sheet of rolled material before it was set into the blanking machine. So I would expect to see that the edge would also get some sort of treatment as well during the burnishing process.
Edited by Dearborn
05/06/2024 07:59 am
|
|
Moderator
United States
189053 Posts |
Interesting example!  |
|
Pillar of the Community
United States
2738 Posts |
This is not a proof blank. A proof blank would show a gleaming surface covered with shallow pockmarks. And a satin finish is imparted by the dies. It's not a property of the blank. Does this specimen show exposure of the copper core along the edge? If so, does the position of the copper core "flip" between the convex portion of the blank and the concave portion?
Error coin writer and researcher.
|
|
Pillar of the Community
United States
6116 Posts |
Thanks Mike! I had no idea to even look at that but yes, the copper layer does show all the way around, but it flips between the concave and convex regions. So I'm guessing that means the original blank was punching in one direction, then it flipped over and was clipped from the other direction? Quite interested to learn more here.
|
|
Pillar of the Community
United States
2738 Posts |
Asymmetric exposure of the copper core is due to one of the clad layers being dragged over the edge of the blank. The convex edge will have the bottom clad layer dragged over the edge of the copper core as the blank is forced through the hole in the perforated base plate. The concave edge will have the top clad layer dragged over the edge of the copper core by the edge of the blanking punch.
Error coin writer and researcher.
|
|
Moderator
United States
96857 Posts |
thanks Mike, great information on what to look for...
|
|
Pillar of the Community
United States
6116 Posts |
That is interesting. Certainly learned something new here, and not just to pay more attention to the edge on clad coin errors. Thanks Mike for the process details!
|
|
Page 2 of 2
|
Replies: 21 / Views: 1,037 |
Page 2 of 2
|
First Page
Posted 05/05/2024 1:08 pm
