I bought this on ebay for $55 and its as old as I am but after cleaning up the potentiometer and the battery connection it works fantastic, its found more leaks than I ever could with bubbles. Found a leak in the bottom on my drivers side tag axle air bag and many more!
It looks like a Ray Gun from my cartoons days.
Can you image pulling that thing out and pointing it at a stranger and watch their eyes, then tell them its a Geiger Mueller tube and your checking for contamination. Ha!