Good answer above, but may I add that my GS# had the bayo lug milled off, [factory] came with 3x9 armored scope, colt mount, colt cheekpiece, and a Colt .22 conversion unit in a case that was designed for an AR as the fasteners are set up for one. It also has NO block whatsoever for the FA bits. Check to see if that one has the steel insert, with the GS# It might not have it. Mine is very accurate, surprised the heck out of me when I bought it. It remains the most accurate AR I own. Very good fit and finish on it, much better then you will find nowadays on about any AR out there. Mine also has the small FC pins. Mine is marked Sporter Target on the lower and the SN is in the GS10xxx range also. It should have the dark grey finish that Colt was using at the time. If you find one at a decent price, it is well worth it to buy it. Mine has been flawlessly running since the day I bought it.