This Krag M1898 carbine shows the receiver in original blue and the mottling of the case hardened side plate. One way you can tell original bluing on a rifle is that the stamping of the receiver shows that the letters and numbers are not blued at the bottom of their stampings. If this were re-blued, the bluing could be seen into the deepest parts of the numbers and letters originally stamped in the metal. You can also see the numerous handling marks in the bluing obtained over 100+ years of being knocked around since originally blued.

The mottling is quite unique in examining Krag parts like this.

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