Appears to be maker's mark WP #370. The symbol looks like the katakana character 'Nu' ヌ above 'Ichi' 一 (a line underneath).
The symbol 'Nu' ヌ is rendered with nicely flaired script.
In Walt Pich's field guide, he observed that this mark has only been identified on tiny 1 1/2 inch floats. This float measures about 2 1/2 inches in diameter, so this float must be quite rare.
It also has a good tight net.