This is a factory Colt A2 upper receiver off a pre94 "blue label" Government carbine (R6520). The receiver has the M4 feed ramps and is marked with a "4" above the gas tube hole. The side of the receiver is marked "C MB". Small front pivot hole. Color is preban (pre94) dark grey. Condition is like new, it was carefully removed from a NIB rifle.
No disappointments, this receiver is absolutely in pristine condition. The reciever is completely original and absolutely has not been messed with in any way, complete with forward assist, ejection port cover assembly, and A2 sight. I'll also include the matching delta ring assembly from the same rifle. I have had this for awhile in the safe, and figure it is time to part with some of my extras.