WW1 Era Brass Military Whistle on Original Chain

I happened across this and it struck me as just the right thing--everyone needs a good whistle, these days especially I'd say. And it is military issue, WWI I believe, which perhaps lends it a bit of extra authority! (Made in the USA too.) On its original chain, which is just long enough to latch as a (quite) tight choker, or more practically to hitch to a belt loop or around the strap of a bag. Or to hang from a hook by the front door, say, easy to grab. Satisfying and substantial, with a good weight to it. 

 17 1/2" long on chair. Whistle itself 1 7/8" x 1" x 3/4". Very good condition, and I've sterilized it so it is ready to whistle!