RJ:  I believe your Krag receiver is drilled and tapped for the Weaver #2 side-mount base (48402).  The #2 base is inexpensive, comes with screws, and is still made.  You also need the Weaver side mount 1" High Ring Assembly (49350), which is also still made.  This mount and rings thumb screws onto the #2 base.  The Weaver base and mount are quite rugged and position the scope off-set to the left.  This is necessary for ejection with the Krag action and is not too objectionable.  It also allows use of iron sights but obstructs the issue safety lever. I bought the #2 base first to make sure it fit my drilled receiver.  I found everything relatively cheap on ebay (try 'Weaver mounts').

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