Oberstabsfeldwebel

Oberstabsfeldwebel (OStFw or OSF, ) is the highest Non-commissioned officer (NCO) rank in German Army and German Air Force. It is grouped as OR9 in NATO, equivalent to a Sergeant Major in the United States Army and a Warrant Officer Class 1 in the British Army. Attainment of this rank requires at least sixteen years since promotion to feldwebel and at least six years since promotion to hauptfeldwebel
In army/ air force context NCOs of this rank were formally addressed as "Herr Oberstabsfeldwebel" also informally / short "Oberstaber".
The rank was introduced in the German "Heer" equivalent to the Marine grade "Oberstabsbootsmann" in 1955, and belongs to the grad group Unteroffiziere mit Portepee.
History.
The rank is a comparatively new rank, and had not been used by any German military prior to in 1955. The Kriegsmarine, did however have a , used from 1939 to 1945.
Rank sequence.
The sequence of ranks (top-down approach) in that particular group ("Senior NCOs with portepee") is as follows: