Thanks everyone for taking a look and for the comments. A die chip is what I was thinking as well, but not from age or Die Deterioration
since this one seems to be an EMDS.
I also posted this to another forum and Bob Piazza (of CC fame) replied :
This die is pretty famous. Since it was discovered, there has been disagreement between people as to if this is a misplaced D mintmark, or a well formed die chip.
I've been very busy as of late but will have a contest in the next couple of weeks and I've got a number of nice prizes lined up. Just have to figure out the details.
Thanks again, stay safe, and enjoy Fathers Day this weekend.
Words of encouragement are one of the major food groups. We need to consume them regularly to thrive and grow.