Ken, based upon first observation, I submit that the individual is native American, but he is wearing a cavalry shell jacket, over cavalry pants with the double sewed inseam. He holds the cavalry saber with some familiarity, the revolver is heavy enough to bend the wrist. In so far as I know with a modicum of certainty the IHG did not receive shell Jackets, most had their own buckskin pants, or at least at first. Your guess that he is from the 14th Kansas seems to me to be best.