Please notice the”E” in LIBERTY. The bottom of the letter is not straight like other 1991 D that I have. Could this be an error?
This is the reverse. Notice the top of coin has a weak strike? If that is the correct terminology, would this be an error as well? Half of “S” and all of “o”
What you see on the Reverse is a minor Struck Through Debris or Grease anomaly. It's when the Die that is used to strike the Blank Planchet gets filled with some substance not allowing certain letters to form properly. In your Cent, the S and the oF.. it's common. I don't really see anything on the Obverse except Wear and Tear issues. The small E probably took a hit. It's a Copper Plated Zinc Cent so the plating could also have been affected somehow.