So Robert asked for an explanation of what I though happened. Here is the message back to him:
In order to understand this, you have to visualize a die.(Coins are just opposite of a die) When you look at a die, the fields are the outside edge of the die. The devices/design are incuse into the die. The rim is created by a gutter on the outside edge of the die.
Note the step down from the outside edge of the I refer to this as the gutter. It molds the edge of the die to create a rim while both dies are inside of the collar:
So the anvil die and the collar are on the bottom of the strike, the hammer die is what strikes down during the strike. When the dies and the collar are all together at a small portion of the strike. The planchet is turned into a coin. The die rises and the feeder finger removes the new coin from the chamber. This can happen several times during a second. so it is quick. So What causes the marks that you are seeing on the coin? The fields are polished and made smooth, but if the die is damaged, the coins will start showing marks. On the area affected on your coin, the damage to the outside of the die would show just inside the rim, but not on the rim. You've seen die dents along the rim before haven't you?
Note how any damage to the fields of the die will show just inside the rim area. But on your coin, the rim is also affected. That tells me that not just the outside edge of the die, but also the gutter area was also affected. Leaving both areas affected. Possible even the collar could be affected. My guess what caused this were the feeder fingers were probably struck. Altering the shape of the fingers. These now scratching the collar, the die and the gutter area. Thus all of these areas were affected. But exactly how, we can say for sure. But that is my assumption. The number of coins affected by this? Hard to say. Was the mint working busy with something else or did only a few coins get affected? I've never seen the mint workers to see if they watch over just one die, or a row of dies. If the machine starts making noise, then the worker would give attention to the machine. So is what I think happened at the mint when your coin was struck. Going back on looking on the accident from the coins view. The die/dies, the collar and the gutter may have all been affected. Hope this helps. I should post this information on the page as well with the images.
Possible a dropped die onto another die that cause a dent on the outside edge of the die, making this type of damage to the die, not all the coin struck with this die will also show this.
On this on it looks like the die was dropped onto the mint room floor, damaging the edge of the die altering the coins that is struck with this die.
This was my solution to what could have caused the marks. But others may have another theory. But that was what came to mind to me.