Several Rifles have been rebuilt, Primarily Vietnam era rifles. Commonly the barrels have been replaced. Some samples of markings uncovered on replacment barrels incorporate: Unfortunately, I am on travel so I am unable to write-up shots from the bolt. It can be MPC engraved. The only marking on the carrier https://lorenzoxabba.tusblogos.com/31382670/the-2-minute-rule-for-colt-combat-unit-rail-gun-45