Grand Admiral a naval rank in one of the highest in the several European navies that use this system, what system are they using?
Military rank Military ranks are a system of hierarchical relationships in armed forces, police, intelligence agencies or other institutions organized along military lines. Usually, uniforms denote the bearer's rank by particular insignia affixed to the uniforms. Ranking systems have been known for most of military history to be advantageous for military operations, in particular with regards to logistics, command, and coordination; as time went on and military operations became larger and more complex, military ranks increased and ranking systems themselves became more complex.
Unterleutnant Unterleutnant (NPA-original abbreviation "Ultn."; en: translation "Under-lieutenant" or "sub-lieutenant") was an officer of the German Democratic Republic's army (e.g. the National People's Army from 1956–1990) of the lowest commissioned officer (CO) rank comparable to NATO rank codes OF1c. It belonged to the rank group of lieutenants or subaltern officers. The equivalent OF1c-rank of the Volksmarine was Unterleutnant zur See (en: "sub-lieutenant at sea").