Rare undocumented mark that has Sa サ on one side of the seal with Se セ on the other side.  Both of the symbols are quite close to the edge of the seal.

This is the only float that has both Sa サ and Se セ mark that I've seen but I've heard that there may be others who have seen this mark previously.  No public photos, though.

The float itself is nicely netted and it measures close to 5 inches in diameter.  It also has a fine amber swirl emanating from the seal.