This extremely rare cast iron mold was used for producing 10 inch glass floats.  It was discovered in Wakkanai, a small fishing town in the far north of Hokkaido Island, Japan. 

It originated from a glass fishing float factory in Toyotomi Onsen where Mr. Maeda was part-owner in a factory with Asahara Glass Company in the early 1930's.  Toyotomi Onsen was chosen as the perfect place for melting glass, since it had a rich source of natural gas.  The joint venture moved to Wakkanai sometime later and eventually closed in the 1970's.  Glass floats made at the factory were sold to Wakkanai, Rebun Island, and Rishiri Island fisherman. 

The 10 inch glass float shown in the picture was produced at the Wakkanai factory and may have been blown in this exact same cast iron mold.  Mrs. Maeda kept this mold for many years until I was lucky enough to acquire it.  I think it's a fantastic part of float making history.