Old sisal netted float with WP #24 'Shi' シ, commonly known as Smiley Face.
The sisal net looks like it still has quite a bit of tar residue embedded in it. There's also some tar speckles on the glass. The net is very fragile and crumbles easily.
This float measures 4 1/4 in diameter (without net).
Found on Hokkaido Island, Japan.