Heavy Medium Credit Box

Heavy Medium Credit Box is a premium class 3 credit lockbox. Upon use, these boxes award credit 639-1117.

Source
Heavy Medium Credit Boxes can be obtained through the Crew Skill Slicing. They can be harvested from Biometric Footlockers on Alderaan, Balmorra (Republic), and Taris (Empire), which requires level 165 Slicing, or from level 25-32 Slicing missions.