Although the Navy’s Military Sealift Command system of officer rank insignia borrows heavily from the Navy, nearly all the men and women wearing it are Civil Mariners, who do not use traditional rank titles in their jobs. Take the silver oak leaf emblazoned with the MSC initial, for instance. A silver oak leaf in the Navy is the insignia for a Commander, second highest of the service’s non-Flag Officers.
In the Military Sealift Command, it also represents a Commander, but Civil Mariners at this rank are given job titles based on their job in one of seven Departments (Deck, Engine, Logistics, Medical, Communications, Culinary, and Purser). Only Engine and Deck Departments have officers at every rank level, and a Commander in Engine Department is called the First Assistant Engineer; a Commander in the Deck Department is known as the First Officer.
The Military Sealift Command’s ships are divided into eight distinct functional categories: Expeditionary Fast Transport, Fleet Oiler, Special Mission, Prepostioning, Service Support, Sealift Program, Fleet Ordnance and Dry Cargo, and Afloat Staging Command.