1968 P And 1968 D Roosevelt Dimes Die Markers

I don't see it. Coincidental post mint damage implies random damage that is not likely duplicated. Both coins have the exact same mark in the exact same position from two different mint locations. It is precise in that the depth and position are extremely close to the rim and does not protrude into the obverse side. I am still researching this and will update if I can find anything to explain it. Thanks for the response.

For sure these rim gouges are damage, but perhaps @hew is right that there is a commonality to it. I'm thinking of the slanted and sheared letter L in LIBERTY that we see on cents previously used in old fashioned gum ball machines. Perhaps some other machine that accepted dimes indented the rims and we've just never noticed that.

Another way to see that this is damage is the way the metal on the edge (the reeded part) is bulging outward from the coin. That cannot happen while it is getting struck - the collar that is in place to form the reeds will ensure that the metal stays put where it is intended to be. A hit after it leave the mint will let the metal bulge out wider than the coin. (see your last picture for clarity, as it shows it best).

The marks are not even close to the same.

I may have found what these marks are. This is just speculation. I ran across an article about how they test for metal hardness. It appears that they attached a ball of metal to a die and stamped a planchet to see if the metal was too soft or hard. This was very tiny and much like the spot on those dimes. The only example I saw was on a penny. It was on the reverse near the center of the coin. Both those spots on the dime looked concave and similar to the one in the example. If this was the case it would explain how both dimes were so close in placement. While both of those notches were a little different, keep in mind that they were from two different mints and could have been done by different people. Like most of these processes, I'm sure they did not intend for any to get into the hands of the public. However, there is a picture of a penny with this mark on it. Here is a link. https://www.error-ref.com/rockwell-...in-planchet/

Silviosi... There seems to very little known about this process. And as far as I have discovered, the hardness of the planchet is the main concern. No one has of yet has been able to give me a reasonable explanation as to what this is. Personal opinion is just personal opinion. I appreciate the responses everyone has given but I am still looking and this is as close as I can get so far. I may never know what caused this but someone does. I'll keep looking and I feel like I'll get an answer eventually. Thank you for your help.

No need to re-invent the wheel. The rims are just following the pattern set by the die gutter. Contact marks are what you are seeing. If on one side of the rim, a hit from another coin. If seen on both sides opposite each other, wire cutters.