I'm not much of an AR guy, so I need a bit of help. I've got a chance to buy a Colt AR-15 A2 style rifle. I've only seen a picture of it. No idea of the model number. 20" barrel, molded in carry handle, solid stock, round hand guards. Rifle is in excellent shape. Has been shot, but not much. Owner says it haven't been out of his safe for years. Can y'all get me into the ball park on a fair price?