I have read on this board from someone, I believe it was David Spragg, who explained how they make the two types of notches. I believe the rounded notches are made with a sander/buffer of some sort while the rectangular notches are made with a circular saw of some sort. Since the saw cuts into a stack generally, the chips in the center will have deeper cuts than the bottom-most and top-most chips which may have very shallow cuts. I believe that is what I have read. You can check the archives if you wish.

Michael Siskin