United States Air Force uniform regulations allow only three designs for tie tacks and tie clasps: the official Air Force symbol, the “wing and star” design, AKA “Hap Arnold emblem;” and rank insignia. Listed as an optional item for wear with regular or pre-tied neckties, tie tacks and clasps are placed midway between the base of the tie know and bottom point of the tie, which must reach far enough to cover a portion of the belt buckle.
In the Air Force, the grade of E-7 has been divided into two rank designations—Master Sergeant and First Sergeants—since the branch was established in 1947. First Sergeants in the Army had been identified by the addition of a lozenge (diamond) to the insignia of grade, but a distinctive Air Force First Sergeant insignia utilizing the same system was not available until 1955.
Following the creation of the grades of E-8 (Senior Master Sergeant) and E-9 (Chief Master Sergeant), First Sergeant positions were established in those grades as well, also using a lozenge to identify the First Sergeants from their same-grade counterparts.
More E-7 First Sergeant Insignia and Devices