If you have the serial # and call Colt they will tell you many details about it such as when it was made, pre or post ban, configuration as to A1 or A2, etc. They did this for me in about 5 mins. and it was free. This was about a year ago, so I can't promise they still do it. For sure, many pre-ban Colts left the factory without the bayo lug as Colt tried to placate the commies by bending over. One thing to check, as mentioned above, is whether the FH is permanently attached or screwed on. FH's are not banned--threaded muzzles are. This only tells if the upper is pre-ban. The markings on the lower tell, but I do not know details on this. Again, Colt can fill you in with just a phone call. Good luck, I hope it pans out and is a keeper.