The maker's mark is a deeply embedded Diamond that is classified as WP #112.
In this mark the elongated diamond is empty. But if you look close at the bottom of the diamond you can see two small diamond shapes rising up on either side of a flat spot in the middle.
This very light green float measures 11 3/4 inches in circumference or about 3 3/4 inches in diameter.
Found in northern Japan.
It also comes with excellent provenance being from the ex-Col. Rich Richardson collection.