I have RIA drawings specifing barrel markings on a brand new USGI rifle and that marking is just not authorized. Indeed, I am confident the higher receiver is Colt, combined with the BCG. It is absolutely the barrel that's questionable to me. That is what I'm wondering. Here's a picture https://colt-combat-unit-rail-gun22849.blogdemls.com/31068188/the-best-side-of-colt-python-6-for-sale