Some additional thoughts:

In the pre-WW1 era, when the 1903 Springfield was the Service Arm and was also offered for sale to qualified citizens, it made sense to mark civilian owned 1903 rifles, (sold to an NRA member by the DCM).

This made it obvious a current Service Arm was rightfully in the possession of the public.

A gun seller, wanting to get more money for an unofficially altered Krag, might fool a buyer by stamping it "NRA" to pass off a 'Deer Hunter Special as something more collectible.

Another possibility is that a seller or owner just marked 'NRA' on a Krag to assure others it was not stolen government property.

With over 11,000 DCM/NRA carbines shipped from Benicia Arsenal, if the arms were marked, they would be relatively common to see.

Whig - I think you should use this interesting Krag as you see fit.