For a long time there have been many discussions ob various subject where it comes up that marks on a coin, usually a high grade coin, are planchet marks. And that they are left behind on the finished coin because of a weak strike. Usually I argue this point and dispute the assigned grade because I believe that they are not left over planchet marks but are instead contact marks. Just about everybody disagrees with me so I decided it might be worthwhile to talk about it. First I figured it might be a good idea to look at some blank planchets just so we all had an idea of what they can look like before they are struck into coins. So here's some pictures of blank planchets. The first 2 are a Sacky blank. The 3rd is a cent. The 4th is a President dollar. The 5th is a dime.
Now as you can see, some of those have some pretty heavy and deep marks on them. Especially that Sacky planchet. But have you ever seen a Sacky with marks like that ? I sure haven't.
Then it struck me that since those who say the marks are left over planchet marks due to a weak strike, perhaps one of the best ways to find out if they are correct or not would be to examine some coins that were guaranteed to have a very weak strike. So how do you guarantee that ? You only look at coins where half of the coin was struck. And you do that by looking at off center errors. Now this is gonna take more than 1 post, so hold off replying for a bit. Here's some pics of those -
Now as you can see, some of those planchets had some really heavy & deep marks on them too. But you get to see part of the coin at the same time. And every one of them, because they were struck off center, were very weakly struck. Much more so weakly struck than an ordinary coin would have been. This is because only part of the metal was inside the dies. But the really weird part is - even though those coins were very weakly struck, and the planchet marks were quite heavy, there doesn't seem to be any left over planchet marks on the struck portions of the coins - any of them ! So where did they go ? I submit to you that this supports my contention that these marks we are constantly being told on high grade coins are left over planchet marks - are not left over planchet marks at all. Because if they were, we'd be seeing them on these off center errors. And we are most definitely not seeing them. As I have said all along - this is just an excuse that has come from someplace, or somebody for assigning high grades to coins that don't deserve the high grades.
Nice try.... Here's the hole in your logic.... There are simply no areas in the resulting off-center coins that are weak enough to not obliterate the planchet marks. To the contrary, off-center strikes tend to be well struck compared to their not-off-center-cousins because the dies are not aligned and thus the areas of high relief on both sides -- what causes the weakness in the first place -- are not aligned relative to the planchet as they are normally. The result is an effective striking pressure much higher than normal. Don't believe me? Fine, but please explain away the marks in the weakly struck part of O in ONE on 99% of Lincoln cents (including ALL of the 50+ examples posted in the guess the grade threads in the US Coin Forum). This is an area virtually always weakly struck, yet on virtually every high-grade example you will find marks on this feature without any circulation/bag marks in other spots. You are 100% wrong on this issue, IMO...>Mike
A great group of pics and explainations. Correct me if I am wrong, but it would be awfully hard to prove or disprove the theory since post mint scratches and plantchet marks would both lack mint luster. Platchet marks because the metal never flowed there and post mint contact marks would have dug through the luster. By looking at how bad some of the plantchet marks are I would think it would be very easy for these marks to remain on the high points of the coin. More so in the weakly struck portions. This should make for a lively disscusion
Good point about the cent letters Leadfoot. ( one note. this discussions seem to be centered around high grade coins. Should it really matter if the marks started on the planchet or not to determine the grade? not in my book, a mark is a mark is a mark, they all detract from the grade. If it wasn't intended to be included in the design then it should be considered a fault)
p.s. as a coin's metal is pressed into the high-relief and typically-not-fully-struck areas, the planchet marks are minimized relative to their state as a plain planchet (e.g. the "balloon effect"). This explains the difference in the general nature between defects in planchets and finished coins with planchet defects that show but are of a smaller number and size than those normally found in the planchet before being struck.
It would be very easy to prove if you had a "before" and "after" of a planchet and the coin minted by that planchet. If you are to believe me, the marks would match. If you are to believe GDJMSP, they would not. I will wager $500 to the charity of GDJMSP's choice that I am correct with respect to Lincoln cents in particular -- the marks in O in ONE are virtually always a product of planchet defects that weren't pressed out by the strike.
So you're telling me that those off center strikes are well struck because the dies are not aligned ? Sorry pal - I aint buyin that. There is no off center strike that can possibly be as well struck as a weakly struck coin where the entire planchet is between the dies. It simply can't be because there is only half as much metal between the dies. Yeah there are plenty of coins that have a weak strike. And some are known for certain areas. But the marks are not left over planchet marks - they are contact marks that came after the strike was long over with. And yes, there are plenty of Lincoln cents without a single mark on the O.
Then me why that Jeff has not a single mark on its cheek when the entire planchet is covered with planchet marks. No Mike - I aint buyin it.
If those off center coins are supposed to be weakly struk, then why are the detais so strong? look at the breast feathers on the Morgan and the steps on the Jefferson as well as the viens in the leaves of the Indian. They look very well struck to me. I will admit at the center of the coin the design gets weak, but overall they look very well struck. On the (off center) 1920 buffalo obverse, you can clearly see the plantchet marks tranfer on the the rim of the struck portion of the coin.
It's not that they are supposed to be weakly struck - they have to be weakly struck. That's just physics. if a certain amount of metal is required to fill a die so that a coin is well struck, and you take half of that metal away - then the coin cannot possibly be well struck. It has to be weakly struck. And yes, you can see the planchet marks at the edge where the rim would be, because that is the most weakly struck area there is. It is the transition point when the die ends.
Think about effective striking pressure on an off-center strike and you have your answer (for example, if the striking pressure is 1000 pounds which results in 100psi on a full-struck coin, and the coin is 50% off center, the effective striking pressure would be 200psi -- because of a constant striking force and a smaller area to be struck -- simple math). Even better, look at the coins you posted and show me the weakly struck areas (the ones that do, not coincidentally, show planchet marks -- for example the Indian's braid on the 1920 buff). Lastly, ask Fred Weinberg. I disagree for the reasons outlined in my comments above. Please show me examples of a weakly struck O on Lincoln cents with no marks. I challenge you that for every one you find without any I will find 99 that do! Here are all of the MS 66 Lincoln cents on Heritage: http://coins.ha.com/common/search_results.php?Ne=16&N=51+790+231+328+75 You also have 50+ examples from RLM's collection to choose from over on the other forum. Have at it...Mike
I'm not 100% sure but my sense is that either the area is fully struck, or the striking pressure is sufficient to obliterate them even in an incomplete strike (ala the "balloon effect" described in post # 11).
You are incorrect, IMO. The reason is articulated in post #17. In short, if striking force is kept constant (as it is in modern coin presses), and area struck is halved, the effective pressure is doubled: Pressure = force / area Using the above formula, if you keep the striking force constant and half the area, you double the pressure. Q.E.D. I agree, but would add: It is also because there's no collar holding the coin in.
