In the days of sail, orders aboard ship were piped on the Bosuns Call, whose high-pitched whistle could be heard against the strongest wind. The Regulation Call, still made for the worlds navies, is made of brass and copper (beware of cheap imitations!).
Both Calls are 4" long, with matching 50" neckchain fitted with a swivel snap-hook. They are supplied in a presentation box, instruction leaflet and history.