This undocumented mark is similar to WP #293 'We' ヱ but there are significant differences.
The first thing I noticed was that it is one complete symbol rather that two separate symbols that do not touch each other. The bar in the middle connects to both sides.
The second descrepancy is the proportions of the mark. In the 'We' ヱ stamps that I've seen, the symbol is nearly as tall as it is wide. This mark is clearly much wider than it is tall.
This float measures about 3 inches in diameter.
It was beachcombed on Kunashir Island, Russia. Kunashir is one of the four major islands in the Kurile Islands just north of Japan.