Rangen av Miles O'Brien var inte konsekvent under sitt utseende på showen.
Från Wikipedia :
During the story progression of TNG and DS9, O'Brien wears black silver-rimmed insignia, or lieutenant junior grade (TNG: "Encounter at Farpoint"), lieutenant insignia ("Redemption, Part II", "Data's Day", etc.), and then black gold-rimmed insignia (DS9: "Emissary"). Sergey Rozhenko calls him a Chief Petty Officer in "Family" (TNG) but he had been referred to in previous episodes as Lieutenant. Eventually, O'Brien receives a distinct senior chief petty officer's insignia and his rank is emphatically identified in "Hippocratic Oath" (DS9).
Från Memory Alpha :
The character of Miles O'Brien, and the exact rank he held in Star Trek, has a history of its own spanning the length of the character's existence.
In thirteen years of the character's appearances, only in the last four was his rank established to be presumably senior chief petty officer (although this term was never directly used on screen). Through various other stages of the character's development, O'Brien was referred to as a crewman, a lieutenant, and various script notes indicated he was a "warrant officer." The novelization of "Emissary" indicated O'Brien held a rank known as "ensign junior grade".
Sidan ger sedan ett detaljerat redogörelse för de led som han höll på de episoder som han uppträdde; På grund av dess längd har jag inte rapporterat det här, och jag uppmuntrar dig att helt enkelt läsa den vid källan.