I realize this is an old post but I thought I might be able to contribute some. I knew a fellow that worked 18 years in the German gun trade. He explained to me that the rear peep sight used in conjunction with the front and rear iron sights sharpens the focus of the front and rear iron sights for those of us with aging eyes. For those of you who have done competitive rifle shooting you may be familiar with the peep sight oculars that attach to your glasses, or for those on a budget a piece of electrical tape with a hole punched in it stuck on you glasses. This is the same idea.

Vlad