Army surplus NOS Colt M16A2/4 barrel assembly

Army surplus new old stock Colt M16A2/4 barrel assembly. C MP NATO 1/7 stamped, chrome lined, O proofmark near extension. NOT date stamped (pre-1996 production) but has F marked FSB. Likely an M16A2 barrel retrofitted during early GWOT surge. Has minor surface rust spots but should clean up easily, no pitting or damage. Has FSB but no sight post. $500