The translation the dictionary gave me was "Fraternitas Militaris, which I am not sure is correct. Can someone inform me if I am getting poor information and, what the correct translation would be?" I should note that the context of this is phrase is for a coin that I want to make for every Brother who has served as an officer (chancellor, vice-chancellor, scribe, treasurer, sergeant at arms) in the Fraternity.
You might consider using sodalitas, rather than the quite rare, but still acceptable fraternitas. For 'officer' in the sense that you require, the best word from classical usage is probably praepositus.
Together, these would be used in the form sodalitati praepositus, literally 'officer for the fraternity'.