This 5 inch Double Ball float has an Inner Ball that's 1 inch wide at its widest.
The inner ball is a bit opaque but that's not too unusual for double ball floats.
It also has maker's mark WP #130 サ. It's a partial mark that can still be made out but it has been sucked into the middle of the seal button.
This float also has some straw marks in glass from the manufacturing process.
Found on Hokkaido Island, Japan.