Below are examples of some intact police whistles. Interestingly, in searching vintage whistles on eBay, I see the words "Regulation Police" appeared on many German whistles.
Why would Houdini (or the Bonannos) have a police whistle in their home? Might it have been for protection -- an early form of 911? But why is this one cut in half? Could it have been used as part of some spiritualist chicanery?
Please share any ideas or insights you might have in the comments below. One last mystery for 2019!