The No 7's seemed to be the last gasp of the American BHO company. The handcrank one I have is very different but also uses that same odd shuttle/bobbin. It seems like they were trying to hit the sweet spot in the new "cheaper machine" market. there are even two versions of THIS American Cathy has. The earlier one has the top leaf tension like mine.
This one is VERY cool. Maybe I should make a No 7 Display with one of all three models known! hehe