Acme 12 brass boatswain pipe - nickel platedIntroducing the Acme 12 brass boatswain pipe nickel plated A boatswain's call, pipe, or bosun's whistle is a pipe or a non diaphragm type whistle used on naval ships by a boatswain. Making a loud, authoritative call, it was traditionally used to pass commands to the crew when the voice could not be heard over the sounds of the sea. Because of its high pitch, it could be heard over the activities of the crew and bad weather. Acme's boatswain pipe could