It looks like a slight bit of machine doubling on the West side of the memorial bldg., and some letters.
Here is my 1983 DDR-001. You will notice the actual raised feature (letters, memorial bldg.)) are doubled. They are the same height, not flat or shelflike. This is actually the most extreme DDR in the whole Lincoln Memorial series. Most doubled die's won't be this extreme.
I can't say exactly what happened to it. Die wear, a good smack, it does not matter what, or when something happened. It is not a doubled die, there is no actual doubling of any letter.