IMO, the "U" is damage that also hit the "S." I'll also bet the "wing" is debris that would disappear with acetone.
I thought the same at first and I did notice the S but the 2 areas in question look raised. I could see a hit from under both letters pushing the metal upwards but a better picture would help to better determine.
Well, now it looks like actual metal; however, die chips rarely (if ever and I've never seen one) have that much "flow." Due to the damage on the "9," I bet the mint mark is also damaged; however that's a lot more metal "pushed over" than one would expect from what made the "D." It would take 2 seconds to tell for sure w/coin and microscope - or a very sharp photo!
Now that's something interesting. Looks like tooling into the die rather than a chip. Don't think RPM either. Neat! "Winged D" it is and I want it.