As promised in a previous post, here’s some pictures of the actual starter motor in the vehicle up close.
This is the view looking into the engine bay from the top. The black lead going to the housing of the starter motor is from the positive terminal on the rear right of the car.
This is the view looking from underneath the car. That fixture from the body shown above appears to be an earth wire as it seems to merely bolt to the frame between the barrels.
I also found this nice video on the principles of the starting motor put out by the US Department of Defence in 1957.
It nicely covers the electrical side of the starter motor operation so it is well worth watching if you are interested.