1981 D Lincoln Penny D Over S Mint Mark Error OMM?

@oso, first welcome to CCF. Second, as best practice is to only start one thread per coin, I have merged two of your duplicate threads together and locked the third one. I'll also move this over to the correct subforum. As noted by @dear, you seem to be missing some brackets on your photo files which is preventing them from showing properly. I'll try to fix this as well so that folks can focus on answering your question.

At first glance, the mint mark appears to have taken a circulation hit--likely a lateral hit which moved/displaced metal.

Logic tells me that it is not possible for a legitimate coin to have both an "S" and a "D" mintmark, since all "S" coins are minted at the San Francisco mint and all "D" coins are minted at the Denver mint.

Would one you experts please explain to me how this can occur?

fplagge,
http://doubleddie.com/58243.html
John1

This looks like a heavy circulation hit.

As mentioned above, it is a flattened device due to circulation hits and dings and bangs