At first I thought it was a die break by how it starts at the rim, through the C and E, up the steps...but then it gets "flakey" looking in a large area to the right, then goes back to a solid line, and the strangest part (or, one of them) is how it "stair-steps" down below the 8th column. Eventually, it all terminates into what looks like a strike-through - as it is the only area that is lower.
Maybe these magnified pictures and a different angle of lighting will help.
Thank you all for your input...this is great.