Standard Medium Credit Box

Standard Medium Credit Box is a standard class 2 credit lockbox. Upon use, these boxes award credit 457.

Source
Standard Medium Credit Boxes can be obtained through the Crew Skill Slicing. They can be harvested from Security Footlockers on Balmorra (Empire), Taris (Republic) and Nar Shaddaa, which requires level 90 Slicing, or from level 17-24 Slicing missions.