Hi All, I came across this penny today and I am having some trouble figuring out what it is. At first it looks like a D mint mark that was damaged. However, under magnification it doesn't look like damage. It looks a square with a horizontal line through it. I can't find anything online about a known mint error fitting this description. It definitely looks cleaner and lower than a filled D. Any thoughts?
Welcome to Coin Talk! It's hard to tell from your pics, but from what I can see, it looks like old damage. It might also be a filled device which was very common in the 50's cents.
It's a 1955-D Lincoln penny, 563,257,500 struck at Denver that year. As Ikandiggit stated, a common filled device from the 50s.