Quite a few rifles were being rebuilt, Specifically Vietnam era rifles. Usually the barrels ended up replaced. Some examples of markings observed on replacment barrels include things like: However, I am on travel so I can not submit pics from the bolt. It is MPC engraved. The only real marking https://coltcombatunitrailgun4533421.blogolenta.com/28147762/colt-m16a1-for-sale-things-to-know-before-you-buy