 Thus, Army, Air Force, and Marine colonels together with Navy and Coast Guard captains wear the silver eagle insignia of the grade of O-6, while Army, Air Force, and Marine captains together with Navy and Coast Guard lieutenants wear the double silver bars of the rank insignia of the grade of O-3.Additionally, the O-6 rank of Navy and Coast Guard captain is abbreviated as uppercase "CAPT", while the O-3 rank of captain is abbreviated as "CPT" for the Army and mixed-case "Capt" for the Air Force and Marine Corps.In the United States, the rank of captain first appeared in the Continental Army during the Revolutionary War.