Welcome to Coin Talk! Please post full image shots of the full obverse and full reverse cropping out any extra border if possible. Right now it looks like you are posting a broken CPZ (copper-plated zinc) cent. Proper pictures will allow us to help you. It would also be helpful if you gave us an idea of what error you suspect is on the coin…imo…Spark
That’s not a D mint mark. Its the start of zinc rot. Very common on cents after mid 1982. Not an error.
The spot at the mintmark area is a stain, there’s another on the coat. I suppose you could argue successfully that a stain on a Zincoln is the beginning of zinc rot, just before the plating fails…imo…Spark
Maybe I need new glasses? NOT! I see a stain. LOL. Welcome to CoinTalk.... sometimes we argue or even shout.