Sterling silver large link chain necklace large jump ring policeman's whistle ?

A really chunky link chain, this has a large jump ring on the end, it works as a necklace but I wondered as the links are so large if it was a watch chain or a chain for a policeman's whistle ? Not marked but it has been professionally assay tested as Sterling Silver. In very good condition apart from an age patina which would come off if cleaned.