The ACME police whistle was the first whistle created by Birmingham engineer Joseph Hudson. His cylinder shaped airfast whistle design contained no moving parts and was apparently submitted in a competition to find a new way for London's Metropolitan police officers to communicate. Tests conducted on Clapham Common in the 1880s found that Hudson's whistle could be heard over a mile away. It was adopted by the Metropolitan Police and has since been issued as standard equipment in over 120 police forces worldwide. The products supplied here are still manufactuered to the original design and, unlike lower-priced nickel plated versions, have a fine quality silver plated finish.