Marine master sergeant
Master Sergeant Calvin was a member of the Confederate Marine Corps. As a marine, he and Sims served as corporals together. By 2488, he was leading the 2nd Battalion's transportation company in the Guild Wars.
That same year, the Confederate military defeated the Kel-Morian Combine at Prosser's Well, and collected a sum of treasure, which was stored in a warehouse under the command of now Gunnery Sergeant Sims.
Calvin hatched a deal with Staff Sergeant Tychus Findlay. If Findlay could arrange with Sims to steal some of the treasure before it could be accounted for by a logistics team, they would split the loot three ways (along with some for Calvin's soldiers and drivers). The pay would be in silium crystals. Findlay made the deal, but it fell through due to him being arrested for an unrelated crime.