On my 98 Carbine is a peep flip up sight mounted on the back of the original sight. It looks original because a very close pro writer for a great gun mag. has one exactly like mine and mine and his are the same military sights and his is a trapdoor carbine made about the same time in 1898. To be honest, I've been trying to find out anything on these sights and even my friend Pete comes up blank, Why, I have no idea!! I have 2 Krags, a 98 rifle and a 98 carbine and a 1902 bayonet all 3 in amazing shape. New to THIS site but was member back in 2011 with a envelope from William Butts and my membership receipt, drifted away due to other weapons in my collection needing research a never ending quest!    Joe L.