Introduced in 1967, the M16A1 (aka the Model 603) would be the standard issue rifle for the United States Army and Marine Corps until the 1980s. Developed from end-user feedback on the M16, the M16A1 introduced the "fenced" magazine catch to reduce the risk of accidentally ejecting the magazine during handling or movement, the forward assist upper receiver and bolt to help close a bolt that is obstructed by fowling or residue, and other minor adjustments. Post front and two-leaf flip rear sights, with early pattern birdcage flash hider, "C MP C" barrel, ribbed round handguard, checkered pistol grip and a two-position telescoping buttstock. The right side of the upper receiver is marked "C H" below the windage adjustment dial, with the Rampant Colt, model marking, and address on the left side of the lower receiver. The selector is right handed, with "SAFE", "SEMI" and "AUTO" positions, all functional, and a one-piece buffer assembly is installed. The bolt and bolt carrier are both black finished, the latter marked "C". Provenance: The Dr. Robert Azar Collection