Hard to tell from the image provided. It looks like it might be a die crack or a lamination error. With the circulation flattening, it is hard to say from the image provided. But I'm leaning more towards a lamination error.
The areas for extra images would be on the 4-5:00 area on 'O' on ONE. The same area at the top of the 'C' at the 4-5:00 area on Cent. That might show if it rises to a point, or, shows a flap of a lamination. That is what I need to see enlarged. (circulation flattening/wear would be less affected on those areas)