Disconnected from the battery, a Model A generator will put up to (possibly) 32 volts depending if you hit that 'sweet spot' where the 3rd brush position maximizes output.
In real life if you paired the generator up to a 6V battery and generated 32 volts, you'd seriously overcharge the battery in short order.
Thus, normal positioning of the 3rd brush is to make the generator generate about 8 volts (say) and maintain anywhere from 5 or 6 to possibly as much as 10 amps (or even a skosh more if you do a lot of starting at night when the engine doesn't get a chance to catch up on charge.) We're not so much interested in voltage because in these ranges, the battery holds it all back to about 6.5 or so (and so you don't blow light bulbs.)
Not sure of what he has left you with his "all dressed up and nowhere to go" generator. He may have been headed for a totally regulated circuit? There are different ways to accomplish the thing most of them done by regulating the generator field and doing away with the adjustable brush altogether.
I'm not sure how Tom does it, but he may keep the 3rd brush and use that output with his regulator.
Take a look at the Ford wiring diagram, which if you zero in on the generator alone, gives you that "stock" wiring. Perhaps you can correlate to this and get your electrical bearings and figure out what you have. Tom (and I with less assurance) will give you clues later as to polarity, flashing the generator, and other details which can undo all your close examination and attempts to make something work.
Wiring diagram at
http://www.webjunk.com/modela/wp-con...amcolor2sm.jpg
The Model A generator is seriously simple, as you can see.
Joe K