http://www.ebay.com/itm/290868768936...84.m1423.l2649
The sight is an 1898 carbine base with a 1902 eyepiece. The 98 sights were only used on 1899 carbines, and most had their sights changed before they left the armory from what I've read.
This same seller had a 96 carbine sight that brought less! http://www.ebay.com/itm/290868766968...84.m1438.l2649
A week to ten days ago I saw a Krag sight bring nearly the same $240+. I did note something unique about that one though. In addition to the serrations or knurling on the side, and right now I can't remember which pattern it had, there were notches cut inside the groove that the pin on the slider rides in.