There are 5 unique codex entries in the Achievement: Titles section on Ord Mantell. They are class specific.
Captain is obtained from speaking with Corso Riggs during "Landing Party" mission.
Codex type: Achievement: Titles | Faction: Republic | Class: Smuggler
Associated Achievement: None
Lieutenant is obtained from speaking with General Vander during "The Sepratists' Stronghold" mission.
Codex type: Achievement: Titles | Faction: Republic | Class: Trooper
Associated Achievement: None
Sergeant is obtained from speaking with Commander Tavus during "Hit the Ground Running" mission.
Codex type: Achievement: Titles | Faction: Republic | Class: Trooper
Associated Achievement: None
the Mantellian is obtained from completing "[HEROIC 2+] Cutting Off the Head" mission. the Mantellian is unobtainable for Jedi Consular and Jedi Knight characters.
Codex type: Achievement: Titles | Faction: Republic | Class: All
Associated Achievement: None
The Outlaw is obtained from speaking with the Republic Shuttle during "Chasing Skavak" mission.
Codex type: Achievement: Titles | Faction: Republic | Class: Smuggler
Associated Achievement: None