did you get it?Colt produced some sporter ar's in the preban days which had no lug.It also might be the 6500 which was discontinued in 1989 Good luck and be safe ..
if you dont please send me his info i'll buy it id like a old green lable colt.
the only parts that are colt only parts is the large front pivot pin found on green lable (pre 89) rifles and some transitional rifles . and blue lable after 89 will use a large pin fire control group and half circle carrier (the carriers are interchangeable though) and most have the sear block installed . so really the only parts to be concerned about and really there is no concern unless you plan to swop out parts is the hammer trigger diconnector and possibly the front take down pin.