I have a Colt AR-15A3, Serial #: LBD012XXX. On the left side it's marked: "Colt AR-15A3, TACTICAL CARBINE, CAL. .223, SER. LBD012XXX". On the right side it''s marked: "RESTRICTED, MILITARY/GOVERNMENT, LAW ENFORCEMENT/EXPORT USE ONLY". I'm wondering if this particular model is rare and what the approximate value is? Any advice is appreciated.