The more I think about the cast lines, the more they bother me. I've looked for examples of cast police/fire/boy scout whistles like it and I can't find one.
One reference said they they did start to make whistles like this in China. I would think they would look at all possible markets.
Maybe there was a toy police whistle that was mold cast. I shutter to think what the metal alloy may have been. So maybe looking into toys police whistles will be useful.
Just a thought.
Daryl