Hi Bon-Scott I totally agree as to dating ... somewhere between c1972 and c1975.
I do not think a 'series 1' or 'series 2' designation is that helpful here, unless we infer that the green handle was first used with the change to Briggs engines (380031) and the removal of the depth lever.
A remote throttle control seems to have been added a season after the introduction of the Briggs (about 1977).
