Keep in mind these die dents are really very small. Were are looking the the coins with a microscope. So even a slight bit of contact of the die, would look huge on a coin. (because we use a scope to see it)
I just saw another set of these marks show up on another forum. I am inclined to think that Ken Potter is correct in saying that there is no point in pursuing the question about their cause, but every time I see them my curiosity gets the best of me!
I can't help it! I keep returning to this question!
I am working on a hypothesis concerning how these die dents happen. If anyone is able to help me by providing comments, photos, or videos, I would be grateful!
I contacted the US Mint and have received a response. They don’t know! (Surprise!) However, they did offer a list of possibilities. One of their most interesting possibilities of where or when this could happen is during the die installation and/or servicing process.
I am thinking that one of the tools with a high probability of causing these dents is a Die Setter Pry Bar. Here is a photo of some Pry Bars:
I have also found some photos of the assembling of die tool kits.
Quote: In my mind a die is just one piece of many that make up for the tooling or toolset process. Remember the mint is a manufacturing or production plant that just happens to manufacture dies to produce the end product coins. The die itself after creation I'm sure is handled more times than we might think. Can go from creation to QC, then to production, then to the tool setter, then to the machine operator.
The last image shows what I was referring to earlier. The die is just one piece of the tooling or toolset. I get the impression some might think the dies are popped in and out of the machine like a bit used in a cordless drill, when in fact theres a little more involved in setting up for a machining process. Thanks, Doug.
Second opinions are always recommended. Rookies thoughts! Backup data often or good luck with the recovery process..... SME advice!
The dent on the coin in the OP has one obvious straight side.The other side seems to fade away. I still think it is possible that this dent could be made by the action of placing the collar (that is the collar, isn't it?). I have an image of the underside of that collar, which would be the portion to come into contact with the coin die. It is what seems like a circumferential ridge which would make contact. (See the white arrow on this image). Seems to me that it is very close to a "fit". There is room to maneuver the collar a bit before that portion reaches the die surface. It would not take but a slight movement for it to drop slightly off center.