Tony, the body and field windings are the same as the 6 volt genys. The difference is the commutator.
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It has twice as many windings and segments. I took some photos to show the difference.
OOPs!! that's is the starter not the Genny. Anyway you can see the 12volt at the top and the 6volt below.
Looks like I forgot to photograph the Genny, so I don't know.
Regards Rick.