Now at first glance it looks like it should be a 1 but that throws the number spacing off .. when I zoomed in I noticed multiple stamps of 1955 going up the right side .. most Are unreadable there is at these one that you can’t mistake . Also what are those diagonal line from top left and bottom right .. is this pmd? And what’s going on with Lincoln’s eye .. Looks like a skeleton. LOL
Looks like a 1951 s. And it's a filled in die. It looks to have a wood grain affect to it too. Improperly mixed alloy. Called a woodie.