No, see post 5. All round back means is that it is the earlier "rounded corners" case with individual diodes. They came both single field (grounded field) and isolated field, incorrectly called 'dual field'. Isolated field was used 70 and later, and sometime around 72-ish?? Ma converted to the newer square back design. It is a well known fact that SOME models of the squareback charged heavier at lower RPM.
