Shift_master:  You have a nicely sporterized Krag.  As others have pointed out,  it is most likely you have a "rifle" action re-barreled with a carbine barrel.  At the time your's was made, carbines used 1899 marked actions.  Your 'peep' rear sight was manufactured by Leroy Rice company, Elyria, Ohio.  It appears your stock was made to dispense with the action side-plate (on the left side).  Unless you luck into a carbine stock, you are probably best off enjoying your Krag as it is.  The 1896, 1901, and 1902 carbine rear sights would all be correct for your carbine barrel.  But you pay a high premium for an available carbine sight.  Carbine stocks and hand-guards are hard to find and expensive.  I would recommend you look into having some type of barrel band put on your Krag to anchor the barrel to the forearm.  Because the trigger guard screws are so close together, Krag stocks tend to split behind the magazine door, unless a barrel band is used.