After exhausting several avenues trying to find the owner's relatives I finally mailed the newspaper in Wisconsin where the school was located and the owner of the ring used to live. After some searching he was able to locate the daughter and the ring will be on its way back to the family tomorrow!
The reporter says he is going to do a story on the recovery and return so I'll post a link if and when that happens. The daughter says she distinctly remembers her mother wearing that ring through the 60s and she has absolutely no idea how the ring ever found its way into the waters off Japan...apparently nobody in her family has ever even been here. Quite a mystery but at least this little memento is heading back home.