Rare undocumented mark that appears to be an encircled Chou 長 symbol, so it would be Maru Chou.

There are some questions about the kanji.  It could be: Chou - head or leader, Osa - head or leader, or Naga - long.  This symbol could also be the Japanese trademark Yagoh.

It's stamped on a 4 1/4 inch float with tons of bubbles.

This is the only known example of this mark known to exist in collections.

This float has excellent provenance having come from the ex-Jim Watson collection.