Need Help Finding Information About 2004-D Lincoln Penny Th

Sorry about the subject title I accidentally posted because my phone likes to do silly like that. However, I'm very curious about the little mark above the zeros in the date. It almost looks like an accent mark.
I'm a beginner and can't seem to find any information about what this is. Even if it's nothing, I'm still excited to find out what this is called and what may have caused it. Thanks!

Coop is one of our community experts. There are a few others you will also get to know. Following them will steepen your learning curve.

Something to keep in mind when learning or experimenting is to do so on a dispensable coin. The toothpick trick should be practiced on a junk coin just in case what you have there is something of regard. Here though you are safe; looks like a well placed gas bubble. When I do th toothpick trick I roll it instead of pushing a sharp tip. Works about the same only it doesn't risk a scratch. A wetted surface also helps.

Have fun in the forums!

I am no expert, but I try to help my hardest. Any questions you have, just post a thread.

The gas under the plating can be in the field or on the devices:

(both images are from the same coin)