(WWII through Vietnam) First Sergeant, informal reference not currently in use. At present, if it is used at all it refers to a Master Sergeant (who is in the same pay grade as a First Sergeant but serves in a more technical capacity). While not the top enlisted grade, a first sergeant is the senior enlisted grade authorized in a company, the level at which most Marines spend their time. Sometimes used as “top kick” (mostly a WWII usage).