To be honest, I wouldnt put much faith in the 5r rifling, lots of folks doing it. With regards the barrel, to be honest, probably aftermarket, the 308 Win engraved on the side and the actual engraving which appears very shoddy. The markings should have been around 6.1 from the front of the recoil lug. The barrel markings on the left side should be, the rep in the oval, the circle M, and the triangle with x or n. The front sight base screws should be 1.125 and 1.688 from the muzzle. With regards the action, the M24 part looks great, the bolt should have the circle m as you look at it, and on the bottom metal. The box mag and follower are M24 specific and not standard items. With regards the action, the circle m on the bolt, are usually the sign its real. With regards the US markings yeah not sure why that was done.