An old "bubble balancer". Last time I used one of these was back in about 1980 when I was putting Keystones on my 76 big-block Cutlass. A friend gave this to me. It was in the garage of a deceased family friend. He thinks the guy possibly never even used it. He had a garage full of useless stuff. Unfortunately, this was the only thing automotive. It has some rust where the H20 got thru the roof. It's a nice piece otherwise.
