It's more of a definitive line, it goes from flat on the face to immediately curved, then from curved to immediately flat on the sides.
It's incredibly minute, but it fakes me out everytime I look at it, to the point where if I hadn't looked at it more closely the other day, I would have said it has a double edge on it.
It's the reason I had to go out in the cold the other night and take the pics. My brain couldn't stand not knowing.