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What caused the creation of these shiny marks on mint state mercury dimes?
ShadyDave
Posts: 2,186 ✭✭✭✭✭
If I remember correctly, @Insider2 briefly talked about this a few months back. Note the contrasting field (almost mirror-like) in front of lady liberty's forehead. I actively collect mercury dimes and I have seen these "marks" on several examples in the field. What caused this during the minting process and what is the mark called?
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The "big Guys" in the error coin business swear these are from feed finger damage to the die. I have not made up my mind yet so for now that's the accepted reason.
Could it have something to do with the planchet before it was struck?
I've seen shiny spots in the obverse fields of BU Mercs quite often. I've also wondered what caused it......
If it was indeed feed-finger damage, you have to wonder why it was almost always Mercs?
This is also quite common on high mint state 1943 Lincolns.
- Bob -
"Central Valley" Roosevelts
MPL's - Lincolns of Color
Not feeder finger scraping damage on Mercs, imo.
I've always thought those shiny areas are from the
Dies being polished to remove clashed die marks,
among other reasons to polish the dies in that area.
for PCGS. A 49+-Year PNG Member...A full numismatist since 1972, retired in 2022
Interesting, can you share a picture of these marks on a Lincoln cent? Anyone else see them on any other denomination of coins?
I think I remember you mentioning that. I included a couple of pictures of what feeder fingers are...now how the heck could these cause damage?
If the marks are from the dies, I would think we would know more about these as they could be seen on multiple coins. I have mercury dimes with them in various locations in the field on both the reverse/obverse. Why would these be more common in mercury dimes and not other coins of the same time period?
The Shiny area is called "Die Burn". As Fred said it is from over polishing of the die.
Ken
I have always been of the opinion that it was heavily targeted die polish to remove clash marks.
Professional Numismatist. "It's like God, Family, Country, except Sticker, Plastic, Coin."
Makes sense that it would be polish from the mint, I'm just use to seeing the raised marks (commonly confused with hairlines) that are often seen in a lot of other series, like morgans.
I like that term for this!
The darkened area around PLUR and between the wheat stalk and UNUM appear dark in photos, but very shiny in hand.
- Bob -
"Central Valley" Roosevelts
MPL's - Lincolns of Color
Great! This is what I ALWAYS THOUGHT also - die polish. However, these marks occur on coins showing no sign of a clash or any reason to be polished. This is an example:
Additionally, when one of these coins is face up, 90% of the time the proof-like area is on the top half of the coin. Whatever that may indicate.
Put me down in the feed finger damage camp. Clash marks tend to appear in certain areas over and over, where the highest point of one (negative image) die face opposes the highest point of the other die face. When the dies clash together, those are the areas most likely to hit together.
These shiny areas never correspond to those clash-prone areas. Have you ever seen a clash mark below UNUM?
As to the Mercury Dime, I believe that those were struck with the obverse die as the anvil die, which is the die one sees affected by feed finger rubbing.
TD
Tom, I'm familiar with Feeder Finger scrapes on coins
for about the past 20 years or so.
None of the nickels, dimes, quarters, or dollars with FF
scrapes in the past 20 years look like the shiny areas
on these Merc. Dimes.
I don't know what FF's looked like or how they scraped
across the dies back then, but if it's the same effect, then the
process , the FF, and how they can potentially over-extend
themselves have changed, obviously ......
for PCGS. A 49+-Year PNG Member...A full numismatist since 1972, retired in 2022
This should be one of numismatics' easiest questions to answer. I've been frustrated over this characteristic for decades!
AFAIK the "feed finger guys" are in the majority. I WANT PROOF!
AFAIK, the feed fingers and the press used in the 1940 -60 era don't look like the one imaged above.
EDIT: Fred, you are correct. If I remember they were more "V" shaped. I never looked closely at a quad press.
Learning
I feel the die has been polished at those points to becoming proof-like. The locations are the same place on Mercury dimes and it is most likely die clash with the fasces. The die polish in front and back is one of the pick up points on the 1936-S over date.
Backing up the clashers:
This clash shows where the dies would have been polished up for reuse.
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In my opinion the shiny areas are caused by repeated travel of the feeding mechanism across the die face.
Note that the feeding finger shown earlier in this thread (from my coin press) is the relatively new rotational ("turntable") feeding style. However, earlier coins stamped on Bliss and other similar presses were stamped using a linear (reciprocating) feeding mechanism.
One major reason why I believe that is the "polishing" marks are ALWAYS oriented vertically in relation to the coin's design. This is be expected since the dies would be mounted in the coin press with the designs oriented to the coin press.
Also, the polishing marks are always seen on one side only - never on both sides (if dies clashed then there would have to be clash marks on both dies - so why don't the polish marks show up on both sides ?).
The picture below shows a circa 1948 Bliss press at the Denver Mint. The blanks are shown being shoveled into the metal "funnel". They fall down into a feeding tube and the feeding mechanism linearly pushes one blank at a time out of the tube into the striking position. If the timing of the feeding mechanism is not correct in relation to the die retraction then the feeding mechanism can come into contact with the die face.
EDIT:
I don't know why the images are displayed in a small size. So here are links to the images as originally hosted:
designscomputed.com/coin_pics/denver_mint_1948_obv.jpg
designscomputed.com/coin_pics/denver_mint_1948_rev.jpg
Agree, I'm happy I asked this question.
I own a very beautiful 1944-P MS-66 FB mercury dime that has this "die burn" on the obv near the date and a clash on the reverse to the right of the fasces going vertically. If the "die burn" was from the die being polished, then why didn't the mint catch the very obvious and notable clash on the reverse?
I unfortunately didn't get the coin TV'd but can go grab it at my SDB next time I have a few minutes. Was thinking of resubmitting it anyway since I think its a 67FB
.
I have a few examples. The first one here shows “die burn” in front of Liberty, but check out the next one — die burn right in the middle of Liberty’s cap!
Put me in the feed finger camp, especially if consistent in position and direction. They always show up on the anvil die. For Morgan dollars, you see two shiny patches develop at the top near the wing tips. On Peace dollars, they show up near the 1 in the date. Polishing out clashes doesn't leave a shiny patch of perfectly parallel lines.
Keeper of the VAM Catalog • Professional Coin Imaging • Prime Number Set • World Coins in Early America • British Trade Dollars
That is a special coin. I don't recall ever seeing one as this. Interesting: A feed finger scrape could not touch that part of the die!
PS I'm sure you can tell the difference between PMD on the cap and Mint die polish - right?
I didn’t notice the unusually placed die polish on the 43S until I got it True Viewed. Yup, that’s definitely die polish through there. I can shoot some closeups if anyone’s interested.
I think a feeding mechanism COULD contact the die in that location in the interior of the cap, especially when the fields around the cap are also ground down like that.
What they said. That is what we used to call them back in my days at Heritage when we were doing some of the super-high-grade Mercury dimes collections such as Joshua and Ally Walsh. I never saw them appear quite similarly on larger silver coins, though, that I recall.
Kind regards,
George
Disagree. Unless the feeder broke and got shoved into the deep recess of the die. Perhaps that explains why I've never seen this before.
Thanks. we know some of the names for this characteristic, we don;t know for 100% certain what caused it. I've been teaching it was due to die polish for decades. When I first read about feed finger damage (2-3 years ago) it sounded like a lot of nonsense to me.
We WILL get the answer eventually. Possibly both?
As I mentioned before, the damage from modern (about 1997 to date)
Feeder Finger Scrapes are very different from the 'shiny' areas on the
older type coins we've been discussing in this thread.
I do not believe that the areas of the Merc. Dimes in discussion are
the result of the Feeder Fingers scraping across the dies, and then
resulting in those 'shiny' areas. Imo, they're polished to remove
clashed die marks.....any many times, only one die was re-polished
and returned to the press, leaving the reverse die, for example, either
with some clash marks, or possibly both dies were removed, but only
one was polished and replaced - the other was simply a new die.
for PCGS. A 49+-Year PNG Member...A full numismatist since 1972, retired in 2022
I have a couple dimes with that in the field but not in the areas shown thus far. In each case it's in the field only. I've always thought it was an area on the planchet not struck up.
I disagree ...
The shiny patches have striations that are ALWAYS oriented perfectly vertical in relation to the coin design. That would happen from a linear feeing mechanism but it would not be the case for die polishing.
I agree with disagreeing. The place they show up on Morgan and Peace dollars are not where the dies collect clash marks. There are also some die pairs where it can be shown how these patches grow gradually over time, with the dies never clashing.
Keeper of the VAM Catalog • Professional Coin Imaging • Prime Number Set • World Coins in Early America • British Trade Dollars
I agree.
The area in question (inside the cap fold) is not a "deep recess" of the die. It is a relatively high point. If the feeding mechanism was oriented at a very slight angle, it could easily scrape away some metal from that point in the cap as well as the surrounding areas of the fields.
Ok I remembered that I posted pictures of the 1944 Merc I mentioned earlier that had "die burn" on the obv and a clash on the reverse. See pictures below. If the die burn is from polishing, how on earth was the clash on the reverse to the right of the fasces not polished away either? Also tell me that merc is undergraded as a 66FB....
Think about this...The planchet is silver gray-white with lots of tiny hits. In areas where it was not struck up, the color is different and all those tiny hits are still on the surface.
In the 70's, I named them original planchet surface impact (OPSI) marks. Check out the center of a Franklin half.
That's why that PL surface could not be caused by strike weakness while OPSI are.
@dcarr,
IF the scrapes on the cap ARE PL and identical to the area on the fields - that is the deepest part of the obverse and SHOULD NOT EVER be touched by feed fingers.
Great to have you and Tom on one side of this discussion. As I said, we will reach agreement on the actual cause one day as this characteristic is common. I'll add that these marks are extremely rare or DON'T EXIST after the early 1960's - at least I've never seen it.
Unfortunately, the guys who would know the true answer are DEAD!
Simple, The reverse die was not touched by a feed finger or polished out by a wheel.
Glad I read this post. Die burn is something I did not know, I've seen it but thought it might have been a weak strike thru. I love this place and a healthy discussion of minting issues. Gobble gobble. Peace Roy
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If that were true, then that area of the cap wouldn't get polished either if the die was lapped.
But the area we are talking about is a high point on the die, higher than the surrounding head.
In this picture (see below) I have highlighted all the scrape areas. These are all consistent with a planar lapping of the die. Something moving across the die repeatedly could easily cause these marks, including the area inside the cap fold. Also note that the striations within the scrape areas indicates that all the scraping was done in a vertical direction in relation to the coin design.
And also, it is not necessarily the case that the feeding mechanism would have to touch the die face to cause this. Repeated sliding of tens of thousands of planchets across the die face could also cause the shiny polished patches.
I'm enjoying this fascinating and respectful discussion. I have quite a few high grade Mercury dimes, and a couple of those have these areas, and I always wondered what was going on.
Gonna get me a $50 Octagonal someday. Some. Day.
But do planchets really slide across the anvil die? It was my understanding that the striking cycle was something like this:
Dies squeeze coin in collar.
Hammer die retracts.
Anvil die pushes coin up out of collar.
Feed fingers enter coining chamber, closed to hold new planchet; forward end of fingers knock just-struck coin off of anvil die, which then begins to retract. Feed fingers continue forward until planchet over recessed or recessing anvil die. Feed fingers open up to release planchet, which falls onto anvil die. Still open feed fingers retract and then close around next planchet.
Once the feed fingers clear the coining chamber, with the anvil die retracted and the planchet resting on in in the collar, the hammer die descends and strikes the coin.
Repeat.
The directions and positions of these parallel drag lines tell me that they can only be caused by the undersides of the feed fingers pushing in over and over and over. The only thing I am not sure of is whether the drag lines were caused by the actual metal on the undersides of the feed fingers (probable), or perhaps a buildup of mint grease and metal particles on the undersides of the feed fingers. The press operator cannot see the undersides of the feed fingers, so why would he dismantle the feed finger assembly just to clean something he cannot see?
Here is my example. I have always wondered. Thanks for the insight on this thread.
You may be on to something. The dies are supposed to be separated to allow a coin to be ejected; however, we know that is not always the case as "ejection doubling exists."
I think you may have the answer! Die burn is normally found on the coin's obverse. That may add a clue.
But do planchets really slide across the anvil die?
Remember that the Anvil Die for a Merc is the Reverse.
Ken
No, the anvil die was the obverse for most years.
My point in the above was that a planchet could not slide across the face of the anvil die if it were recessed any amount in the collar. The collar would prevent any lateral movement.
Sorry, my mistake. Reverse was the hammer die.
Ken
As a planchet is being pushed into the collar, it can tilt and touch the die as it is going in.
Regardless, my opinion is that the shiny marks are caused by contact with the actual feeding mechanism.
@dcarr said: "As a planchet is being pushed into the collar, it can tilt and touch the die as it is going in.
Regardless, my opinion is that the shiny marks are caused by contact with the actual feeding mechanism.
I like this. Because, after a certain time period, "die burn" is non-existant on any coin! We know the feeding mechanism and press type has been changed.
Be sure to see Mike Diamond's Collectors Clearinghouse article on die abrasion in the Dec. 16 Coin World Online that just came out yesterday. Fascinating!