This is 1955D-1MM-004. The other mentioned die, 1955D-1MM-002, has much better definition to the doubling on the bottom of the mintmark.
The swirl inside the mintmark has no corresponding relief on the outside of the mintmark, but somewhat interestingly has the same depth and basic characteristic of a die scratch evident to the south of the 9. That's the way I would lean with this...since the 'third D' does not have the size or shape of a D, and that there are other die scratches in the area, this is likely a scratch too.
This whole thing is about attention to the finest details.
The swirl inside the mintmark has no corresponding relief on the outside of the mintmark, but somewhat interestingly has the same depth and basic characteristic of a die scratch evident to the south of the 9. That's the way I would lean with this...since the 'third D' does not have the size or shape of a D, and that there are other die scratches in the area, this is likely a scratch too.
This whole thing is about attention to the finest details.




















