Automated Personnel Unit 6263 was a Pralor Command Unit assigned to a Pralor vessel during the 2370s.
He politely thanked Captain Janeway for returning Automated Unit 3947, but after 3947 abducted B'Elanna Torres, he threatened to kill her if she failed to reproduce a prototype unit. (VOY: "Prototype")
6263 was played by actor Hugh Hodgin, who also played Prototype Unit 0001 in the same episode. The Star Trek Customizable Card Game gives its name as Pralor Unit 6263.