This 3 inch glass ball is unusual for a couple of reasons.

First, it has a pinched end instead of the normal seal button.

Second, it was manufactured in the three-piece molded construction method.

It has been speculated that this could been an experimental design.

There are quite a few signs of use, so I think this was probably a working float.

Found in Northern Japan.

This float has excellent provenance having come from the ex-Col. Rich Richardson collection.