Using the codes from John Smith instead of the 65 and later codes it can make sense other than he doesn't have the G listed.
1=Ind. and Ag after 1963
1=4 speed with PTO
The model code would seem to match your tractor this way even though many of us haven't seen those tractors built that late. Just goes to show that we can all learn from each other if we continue to follow through with gathering information to help each other.
Nice find by the way!