1931 S Lincoln Penny

I'd welcome a sharper photo and closeup of the date and mint mark, too. Here are marked comparison photos from the OPs coin and a known genuine coin. One caution and two concerns. The caution is that the OPs photo is dark, and doesn't clearly distinguish between shadow and the design element at the base of the first "1" in the date. This could throw the lines off just enough to make the coins look different. The concerns are the angle of the top curl of the "3" and the alignment of the middle bar of the "3" with the diagonal from the "1" and the bottom of the curl of the "9" in the date.

Clearer photos could resolve the concerns. I'm certainly not able to make a call with the photos, but I am pausing on this coin.

There are two diagonal lines on the OPs photo. The red line is where I think the bottom right of the first "1" is located from the photo and the aqua line is where the bottom right of the first "1" should be. The implications are quite different. A clearer picture with a little bit more light on the surface would definitely help. The top curl of the "3" is still a concern, though.

I tend to agree on a long acetone soak and then a Verdi-Care application . If done right all that crud should come out . Then take your close up photos .

Can you show us some of them ?

Hummm....I like the crud, I'd leave the coin just as it is. It has a very honest, original look to it.