They had finally gotten around by that time to repudiating the fact that O'Brien was an officer during the early part of Star Trek: The Next Generation. ProfessorTrek 20:14, July 30, 2011 (UTC)
The "weird thing on his collar" is his rank of senior chief petty officer. The character originally started as a background crewman. As the role grew he was given a last name and his rank specified as an enlisted rating, hence O'brien's rank flutuating in the early seasons of tng although he was always addressed as chief when he worked in transporter room 3.