Here's one on the Google images, sorry about the size I don't know how to fix that on this website.
Not saying you don't have a valve mark there somewhere. But I think what is pictured is mostly heavy carbon buildup. When I had a piece of aluminum scrap in the combustion chamber of the b58, it didn't mark the pistons, but it made markings in the wet carbon build up that was on the pistons, and looked really scary through the camera. You can't really see anything in those cameras. At least I can't.