Acme thunderer bakelite arbiter flute

Special vintage, The Acme Thunderer, arbiter flute. This is a bakelite version, marked on the front and back, on the back is Acmeoid, England. In which competitions would this bakelite arbiter flute be used? Nobody can figure that out. The second whistle on the photo is also a vintage arbiter whistle, an official N1 B arbiter whistle. Both arbiter whistles are in used vintage condition.