During WWII and Korea our troups needed gas as much as they needed bullets. It was up to the Corp of Engineers (in which I served just after the fighting stopped in Korea) to get gasoline to the front. Gasoline was brought up in tankers, but they couldn't go all the way to the front to fuel the tanks, so the gasoline had to be put in what we called "Jerry Cans." Every military vehicle had a place where one or more Jerry Cans were attached, including the Jeeps.
Since it was necessary to download the gasoline from the tankers to the Jerry Cans 24 hours per day, it was very hard to determine when a Jerry Can was filled in the dark. At this time Wheaton invented the "Whistle" nozzle. It would whistle when the gasoline reached the top of the Jerry Can.
That is what you found.
Not many of them around, didn't go with any pump, but since you now own one and know the history of the nozzle, it will be a great conversation piece with your friends or fellow collectors.
In a week or two, I will begin a new series of posts that I will be calling "FOR YOUR INTEREST." One of the thing I will be posting is pictures of our GIs in Korea filling Jerry Cans using the nozzle you have.
Author, Gas Pump Identfication books 1st & 2nd Editions & Air Meter Identification books