Not able to sell it

I got this armour from the guy i killed in Armory but i cant sell it eventhough its 53/56 HP.No explanation also why its not possible.Maybe because its some kind of"Officer skin"

I got this armour from the guy i killed in Armory but i cant sell it eventhough its 53/56 HP.No explanation also why its not possible.Maybe because its some kind of"Officer skin"