the fifth ship to be named "mercury" by the navy, "ak-42" was launched as ss "lightning by federal shipbuilding & dry dock go., kearny, new jersey, 15 july 1939; sponsored by mrs. royal s. copeland; purchased on the ways by moore mccormack lines and placed in operation by them as ss "mormactern 30 october 1940; acquired by the navy 20 june 1941; converted, and commissioned as "mercury" 1 july 1942, lt. comdr. g. w. graber, merchant navy (united kingdom), in command.