I discovered a number of variations when I looked. Some have been marked M-16A1, and several were being marked M16A1. Some had SERIAL essentially stamped on there before the serial range, and Other folks didn't. It's got the early reciever without any fence throughout the mag release and all early https://colt-python-6-for-sale47754.wikiitemization.com/4607920/what_does_colt_combat_unit_rail_gun_45_mean