'Whig' - I took the liberty of cropping and marking (with arrows) some of the anomalies I noticed on your Krag's photos: (evidence of reduced diameter barrel and faint letters from previous stamping).

I also attached a photo of the N.R.A. stamp found on some civilian owned pre-WW1 1903 Springfield rifles.

The breech end of your barrel and the quality of the extractor-cut might be the best clue that it started out as a Krag barrel.

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