This version of mark WP #344 'Wa ワ Under a Roof' has a set of two marks that mirror each other.
It's less common than the single version. There have been several floats with the 'mirrored marks' identified in recent years.
This float has a nice yellow swirl that eminates from the seal. There are also some tiny remnants of shell life.
It measures about 3 1/2 inches in diameter.