Whig - Interesting pictures, you posted, showing the remains of barrel markings.

IMHO - Your barrel did not start out as a Krag barrel.

It likely was a 1903 Springfield, 1917 U.S. Rifle, or machine-gun barrel, that got turned-down, threaded, re-chambered, and 'slotted' for the Krag action.

The machine marks, from being 'turned down' on a lathe, are obvious.

I am sure the NRA stamp is bogus. Likely, the first attempt on the butt-plate looked so fake, that it was polished off and re-stamped.

FWIW - The DCM was established in 1903 and placed under the U.S. Army in 1916.
The N.R.A. stamp, found on some 1903 Springfield rifles, appears to date from March, 1915 to 1917, per author Bruce N. Canfield.

The Benicia DCM/NRA "carbines" appear to date from the 1925 to 1930 fiscal years. Mallory reported 11,245 rifles converted in the Benicia records he found.

I am unaware of any special markings placed on DCM sold rifles and carbines.

I suspect some enterprising individual (aka - FAKER) marked your "carbine", NRA, in an effort to pass it off as a (Benicia) DCM cut-down Krag.

BTW - Your rear-sight screws look good. Are the rear-sight holes the correct Krag thread?