The battleship-gray, 85-foot military craft bristling with four .50 caliber machine guns observed navigating the waters off the Orange Coast is a head-turner. What spectators lining the shore see churning through the Pacific waves belongs neither to the U.S. Navy nor Marine Corps. It also has no name. Its only markings are “U.S.A.A.F. P-520,” painted in black on the stern and both sides of the forward pilothouse.