We often see these on coins that are found in a parking lot. The same alters the coin, when they are ran over by coins. So a single grain of sand can leave an incuse mark on a coin. Note on the 'N' the two incuse marks there are called bag marks. They CAM
from contact with other coins during its life. Sometimes the damage is so strong it makes a wave that is seen on the coin:
These are clues for post strike damage to a coin. The metal movement has to go somewhere. Then like pushed snow, it rises. This tells me that this happen post strike. Even Machine Doubling
pushes the metal aside and creates a wave:
Note the moved area and the pushed aside metal on this proof coin. Even damage to coins can be noted. by pushed metal during a coin scratch:
Note the trench that will have a flat bottom and the moved metal in this case is plating, it is moved and rises above the surface of a coin. This is post strike damage to the coin. It is not a mint error, but coin damage. No premiums for coin damage. If there were, then we would have no change. But as a face value coin it will eventually get to a bank and then be sent off to be canceled and recycled.
So why is this information helpful? 99% of incuse marks on coins are coin damage. If you see a bent coin, this damage is post strike. As mention already the wavy is noticed on some coins. Why this is not a mint error, is that if a mint error happened during the strike, the wavy would never happen. The dies would prevent the wave. The struck through object struck through would be on the coin and show no wave because of the dies/collar working together. What types of mint errors could be seen? We will limit this to the common events to show why is different about a struck through item.
Struck through wire:
Note the shape of the trench? On the previous coin cut with a knife, we would see a flat trench. Note on this coin. The trench is rounded because of the shape of the wire. On the struck through area the wire was drowned by metal and was held in place during the strike by the collar and the dies. Thus we see a contoured trench.
How to tell if this is a mint error? Note the strong ends to this object struck through? That is a clue for it being a mint struck through error.
Wire can be bent and this example shows the same beginning and end with a definite start/ending of the wire that was curved. No wave was created, so this is a mint error. There is even a back mark also on this coin.
Struck through string:
Note on this one the string collapsed, but you can still see the texture of the string. Note it is wide and there is no wave created with this mint error. Same for struck through thread, but the thread will have more movement on the struck through:
Even a knot is noticed in this piece of thread.
Struck through rim burs:
Breakaway and struck on the same coin, from the same coin.
Even a huge rim bur leaves not wave. Because if happened during the strike.
The die/collar contained the strike to an isolated area. So when you see a wave of metal movement on a coin, it happened after the strike. It is just post strike damage to the coin. Not a mint error. Hope this helps? CoopHome
: How can you tell if something is a mint error or post strike damaged?