Three Chief Petty Officers instructing enlisted students in a sub school classroom, circa 1943. Note diagram of "fleet"-type submarine tanks and arrangement on the blackboard and "Be Reliable" sign above. Plaques on left indicate that these chiefs may be: Chief Torpedoman's Mate J.F. Affeldt, Chief Boastswain's Mate R.E. Hopfer, Chief Machinist's Mate L. Vannauker.