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 Replies: 18 / Views: 3,031 |
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New Member
 United States
45 Posts |
Ok I got some pictures. I found out the marks are grain lines. The mirror polish makes the slightly wider grain lines more reflective. Original thread: http://goccf.com/t/431069  Coincidental that a visible grain line is behind Lincoln's head. |
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Bedrock of the Community
Canada
21603 Posts |
Who told you they were "grain lines"?
They look like linear plating bubbles.
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New Member
United States
45 Posts |
Under a microscope, the marks are parallel with the grain.
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Bedrock of the Community
United States
94367 Posts |
Parallel with what grain? There is no grain on a cent.  |
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Pillar of the Community
Canada
5239 Posts |
Quote:
Parallel with what grain? There is no grain on a cent. Yes, the last grain on a cent was in 1958! |
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Moderator
 United States
95654 Posts |
linear plating bubbles, is what I think it is. above Liberty it looks like roller lines - which I think can trap zinc dust before the plating process. The zinc dust can expand and create the bubbles.
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New Member
United States
45 Posts |
Not grain as in wheat, grain as in the crystalline structure of metal. I'm talking about grain like in this picture of a knife. Coins can have grain like that but not always visible to the naked eye Dearborn, I've looked at photos of linear plating bubbles and saw some coins have a wood grain appearance at the naked eye. My penny doesn't have that unless under a microscope. The marks on the penny are concave and at first I thought they were convex.
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Moderator
United States
56855 Posts |
On the knife is 'grinding" lines,part of the sharping process. On your coin is a copper plating issue. John1  |
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Moderator
United States
95654 Posts |
Quote:
The marks on the penny are concave and at first I thought they were convex. so you are saying that the marks you circled are incuse and not raised? Can you try to post up better pictures without the glare? Use only one light source from the side if possible. |
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New Member
United States
45 Posts |
Dearborn, here's some pictures of the penny under a microscope with front and back lighting. Top and bottom pictures are of the dimple by the date. The middle pictures are the line behind the head.   
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Moderator
United States
95654 Posts |
thanks for the new images, but you need to focus the scope on the field not the higher devices to see what is going on.
I'm also curious as to why your imaged are mirrored (backwards).
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Pillar of the Community
United States
1648 Posts |
The images do seem to most closely match linear plating blisters as suggested. https://www.error-ref.com/blisteredplating/ (rather than roller marks). Roller marks by comparison are lines caused when specks of dirt, grease, or other contaminants adhere to rollers which press planchet strips to a desired thickness. The debris is normally pressed into planchet metal forming incredibly straight, linear, fine parallel lines as the planchet strip is fed through the rollers. This effect is quite common in copper-alloy cents from the late 1970s and early 1980s. These coins do not show the cracking and peeling commonly seen in improper alloy mix errors. Roller marks are quite even while improper alloy mix streaks tend to vary in width. Roller marks are easily worn off while improper alloy mix streaks extend much deeper into the coin. Keep in mind that roller marks can appear on any coin - even improper mixtures or perhaps here as well. Edited by datadragon
09/26/2022 12:55 am
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New Member
United States
45 Posts |
I'll see what I can do Dearborn. The protector case is making it difficult to focus. The images are backwards because the microscope inverts images and I forgot to reverse it with the photo editor.
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New Member
United States
45 Posts |
I'm no longer interested in this thread. Thanks everyone!
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Bedrock of the Community
United States
19945 Posts |
Those are plating bubbles, nothing more. Proofs are made using the same planchets as the business coins, they are just polished an extra step in the planchet preparation process. Sometimes you get a stinker!
Edited by BadThad
09/30/2022 6:57 pm
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Posted 09/24/2022 5:03 pm
