http://varietyvista.com/Variety Master Listings/lincoln rpms 1940-1941.htm Check your coin against the listings for 1940S
I believe it is PMD ( post mint damage) as the underlying shape top and bottom is much wider than the stronger image. Since multiple strikes of the mm on the die did occur at times, the same punch was used, and any suspected secondary mintmarks should have the same shape and size. I look at the obvious mintmark and turn it around in my mind ( some use photo techniques) to see if its stays within the shape and size of the primary. I can't see that here. The top and bottom of the top S seems to have been hit somehow through circulation to flatten. IMO, Jim
Thank you for posting full image photos and welcome to CT. Close ups of the date and MM would be helpful.
The five o'clock position of the lower portion of the S shows a thin body caused by a PM strike of another device. Not a RPM.