I have both bored and original 6P. I looked again and the original doesn’t have the lip. So it’s probably just visually bad machining from Surefire.
I was asking because the original Surefire 6p, 9p, C2, .... does not habe this lip because of the inner diameter of ~16-17mm. The spring of the P60 dropin is on the side ring of the body. There is no lip.
If someone bored a body in a good way at the end of the body at the head the tube is not completely bored because of 2 reasons, the 18xxx cell will not fall out the body of the head is removed. The spring of the dropin is now on this lip. Without this lip you may habe contact problems depending on the dropin.
For example Oveready was always boring with lip, even the 3xCR123 bodies.