Colt AR-15 "SP-1", .223 cal. semi-auto rifle.  Serial #SP58868. mfg. 1976.  Excellent condition.   Nice example and looks like a Vietnam era M16 with triangular forearm, bayonet lug, no forward assist, hollow pistol grip, fixed buttstock, 20" bareel with an excellent chrome bore.  Solid carry handle.  This beauty is very clean with 98% parkerization.  Black web sling and a Colt 20-rd. magazine.  These are super light and maneuverable.  Great one to put away. Collectible!