psteinmayer:  The aftermarket rear sight on your sporterized Krag appears to be a Redfield No. 102-k, which was made from about 1930 to 1964.  It looks like someone put extra tapped holes in the top (for some purpose?).  The sight base is held on by an extra long side-plate screw (supplied by Redfield and desireable, since they are often missing from loose sights that are for sale).  The sight base is also anchored by a sheetmetal  bracket that hooks into the hole normally occupied by the magazine cut-off.
  Your Redfield sight is still serviceable and could probably serve you well if you got a screw-in peep disk (easily found).  The Redfield Sight also is suppose to have a flat piece of sheetmetal that mounts under the "coin-slotted" side adjustment screw and serves as a cover and indicator for the vertical (elevation) index marks. 
  The vertical screw in the slide of your Redfield sight is a replacement.  It is intended to hold an adjustment so that the slide can be moved for Bolt removal and then returned to it's sighted-in setting.
  It would be relatively easy to fit and pin a blade in the front-sight base of your Krag.  In the old days, blades were often fashioned from Silver Coins.  It appears the slot on your Front-sight Base has been widened for a homemade blade. 
  For very little money and effort you could rehabilitate and make useful the Iron Sights on your Krag Sporter.  You have a nice Krag Sporter for hunting and the Rifle Range.