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Marks on planchets can survive strike
By F. Michael Fazzari
July 14, 2017

This time I’ll write about both damage and the mint-made imperfections we can find on our coins. When you have an understanding of these defects, you’ll be able to answer 99 percent of the most common questions asked by non-numismatists about their pocket change. The defects we find on coins either happen at the U.S. Mint during production or after they are made. Anything that happens to a coin after it is struck is called “Post Mint Damage” (PMD) by the Internet experts.


Quite a few years ago, Alan Herbert, divided the imperfections we see on “error” coins into his “P-D-S” System.  The “P” was the planchet and the things that could occur to it. The “D” was the die and the “S” covered the actual process of striking the planchet into a coin. I’m going to leave out any marks found on coins due to the dies for another column as these have their own characteristic look. With a little research, readers will probably find all of this is covered on various websites. I would look the best ones up and list them here; but if I did that, I would read them and if similar wording slipped into this column, I’d be accused of plagiarism!


As we were not on the floor of the mint when any of the operations I describe take place, all we see is the result of the mint-made imperfections – what they look like on a struck coin that has been released into circulation. Let’s start with the planchet; but even before that it was called a “blank.” The blank is a flat disk that was punched out of a strip of metal about the thickness of a coin. If all goes well, the blank will be complete and round. In the case where the strip did not advance properly in the blanking press, the planchet will be incomplete and cut improperly (clipped). Most of these imperfect blanks are removed before they become coin planchets. A blank may have impurities that were left in or on the surface of the strip. Imperfections on the surface such as “roller marks” look like scratches into the surface. Improperly mixed metals of different colors and hardness making up the strip appear as streaks or globs. Virtually all debris on the blank is normally washed away before the blank is “upset” and becomes a planchet. Any foreign debris from the strip that is trapped in the interior of the blank will go undetected at this stage. During the 18th and 19th century gold and silver planchets were checked for weight. If they were found to be overweight, some metal was removed with a coarse file. This left scratches in the surface of the planchet called “adjustment marks.” Now our planchet is ready to strike


It seems almost anything can occur when a planchet is struck, either by accident (mint error) or by the intentional aid of man (mint error?). We can find all sorts of unusually shaped coins. Many of these are termed mint errors. An above average website to learn about error coins is ErrorRef.com. In many cases, coins can look unusual due to damage. I once was accused of being insensitive when I suggested a new collector take some pocket change and bang it with a hammer, gouge it, etc., in order to see what a damaged coin looks like.


I would say that the main difference between a damaged coin and one with mint defects is originality. Let’s go back to the production stage and the planchet.  Anything we do to that disk will be “into” its surface. That includes adjustment marks, roller marks, and marks made as the planchets are riddled and tumbled together during washing. Thankfully, most marks we see on a planchet are obliterated when it is struck. Those that do remain generally did not come into full contact with the dies or were too large to have been pushed out by the force of the strike.  I named these “dings” Original Planchet Surface Imperfections (OPSI). You can see what they look like around the ear on a Kennedy half dollar in Figure 1.


With experience, magnification, and florescent light, it is very easy to determine if a mark on a coin originated on the planchet or is Post-Mint Damage. The quickest way to learn what PMD looks like on a coin is to take my suggestion and mark up a brand new Lincoln cent. Gouge and stab it with a nail, scratch it with a pin, and brush it with a stiff wire brush. In each case the surface of the mark will contrast with the coin’s original surface. Additionally, the edges of the damage will usually be slightly raised above the surface from the displaced metal.  Marks on the planchet that were not struck out and remain visible on a coin will have smooth edges and their interior will have a similar color and the originality of an unstruck planchet. Any voids on a coin that were mint-made will look rough and granular inside the hole.


One other commonly encountered mint-made defect is called a “strike through.”  These occur when some debris gets between the planchet and the dies as the coin is made. Until a little after the turn of the 19th century the planchets of many of our coins were dried in sawdust. Occasionally, dust particles remained stuck to the planchet’s surface after it was dried. Evidence for this can be seen mostly on silver dollars. If the debris is still attached to the coin, you will see it.  If it has become separated, it will leave its impression into the surface.  That spot will also have an original surface the color of the original planchet.  Figure 2 shows a magnified image of this type of defect.  Part of the wood chip is still attached (dull tan color) and part has broken away leaving a fresh bright depression with a wood grain pattern. A more commonly found defect is the tiny, shiny struck-through spots seen on the frosty surfaces of our modern coins such as silver Eagles.  Again, the key to separating them from PMD is the originality of the spot under magnification.


As for grading coins with mint-made imperfections, I’ll leave that for another column when I write about the “D” part of Alan Herbert’s system.



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