The rank of Lieutenant, junior grade or an equivalent Civil Mariner position is not listed in the Military Sealift Command Civil Service Mariner Handbook published in December 2016. Instead, the rank insignia chart goes immediately from a single gold bar—an Ensign in the Navy—to two connected silver bars, bypassing the single silver bar of the Navy Lieutenant jg.
Civil Mariners, however, typically do not use Navy rank titles as they are not members of the Armed Forces. Instead, the organizational structure for officers has essentially been reduced to four levels with five insignia: the aforementioned bars, a gold and a silver oak leaf, and an eagle for the title/rank of Master or Captain. Subordinate officers are typically named with a numerical identifier—the lowest Deck officer, for instance, is simply known as a 3rd officer, while the lowest-ranking officer in the Engine department is designated Third Assistant Engineer.
Regardless, the fact that the Military Sealift Command employs the same rules in insignia creation as the Navy—silver always indicates a higher rank than gold, and two bars always outrank a single bar of the color—makes it easy to determine that this insignia reflects a rank or title above the Ensign/Third Officer and below the Senior Lieutenant.