M3-OB was a Astromech droid companion of the Smuggler Zale Barrows during the Galactic War. During the Invasion of Belsavis in 3641 BBY M3-OB was with Barrows on the surface when the rioting started and Barrows decided to stay to ensure the most dangerous prisoners do not escape. Pursued by Zale's old nemesis Skadge and a bounty hunter hired by Darth Tormen, Barrows and M3-OB tried to escape by separating themselves behind a force field. However, the hunter disabled the generators maintaining the field and Barrows was forced to flee, leaving M3-OB behind to be destroyed by Skadge. The Houk and the Hunter were later able to retrieve Barrows' destination from M3-OB's databanks.