1901 Krag Rear Sight Lock Knob Screw (Curved Face for Bottom)
1901 Krag Rear Sight Lock Knob Screw (Curved Face for Bottom)
Original Model 1901 Springfield Krag Rifle or Carbine Rear Sight Lock Knob Screw. This is the one that goes in from the bottom of the base that has a curved face for the contour of the barrel.

