Generator drive Scout 1920-27
Click for bigger pictures.

Broken mounting flange (there was a reason the factory added two mounting bolts for 1928), but otherwise nice and complete.
I am pretty confident that the mounting flange is the only real difference between early and late versions of the drive. Except the case (body, housing) with its different number of bolt holes, all the other parts seem to have the same numbers in the 1920-28 Scout and 1930 101 parts books (20B610 and 20B611 for the two internal gears).
There are several ways of repairing the flange. You should be able to make it with two bolt holes for 1920-27 or four for 1928-31.
See pictures of 1920-27 and 101 primary covers below.

Braze/solder repair on the other side doesn't stand out too much.

Another view. Much of the color is reflections from surroundings. Plating is still pretty nice.

Compare flange to the pictures showing where it bolts to the primary cover. Color reflections in the shiny plating again.

Gear teeth look good.
New bushings for the shafts (and the shafts dressed if worn out of round), a new gasket and new screws may be the only parts needed.

1920-27 primary case/cover with two bolts for the generator drive.

1928-31 primary case/cover with four bolts for the generator drive.