Perfect stamp of WP #319 'Me' メ Ichi 一 (with hash mark below).
In his book 'Glass Ball Marks', Walt Pich states that "The mark has been found on the sealing buttons of light blue 3.5 inch glass balls." This float is almost 5 inches in diameter and may be the only known example of WP #319 in the 5 inch size.
The glass ball itself is quite beautiful. It's a lovely light blue color, there are swirls in the surface of the glass, and it has a 'orange peel' type dappling on the bottom half of the float.
Found on Hokkaido Island, Japan.