I recently purchased an M1 carbine that appears to have been rebarreled. The barrel has a smooth, blue-grey finish with no visible markings on the exposed metal; however after disassembling the gun I can see a faint "flaming bomb" mark with an "S" stamped next to it on the side of the barrel that holds the gas piston assembly. Can anyone tell me who might have made this barrel? A muzzle wear gauge reads .0. Thanks.