In my research of this piece there seems to be a difference of opinion regarding the publisher: was it Watanabe as some insist, or privately published? If Watanabe, why don’t any copies have Watanabe seals? Other pieces by him contain the Watanabe seal, just not this one in any instance I can find.
At the same time, my copy has the seal included here stamped on the verso. Is anyone familiar with this seal?