Found what looks to be a "D" in lincolns neck?

Hello just looking through some rolled change I got from the bank. I found what looks to be a "D" in lincoln's neck with a rounded line curving through his face anyone have any idea what this could be?

 

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Follow the line in his jawbone to the left and there is a D

 

If this coin is newer than 1981 and I believe it is then what you are seeing may be zinc rot.on the copper
plated zinc coins the zinc will start to rot under the copper plating and swell the copper up into all kinds of
different shapes. I think I can even see some of the zinc rot in the center of what you think may be a D.

 

Look at the date style...

 

Thanks I thought that could have been a possibility because it seemed to be a silver color in the middle of the D thanks for the input.