Wiring Regulator Help

Have just put a new bearing in this 6v Generator for Jen. It has been reco-ed recently so every other thing is still OK.

But, this has three wires sticking out of it not 2 like all the other ones I have seen.
The fat wire in the center comes straight off one of the brushes. I assume the wire on the right goes to terminal 51 or F. What about the one on the left ???
Got me stumped.
Help:o

Just had a look at mine, and the fat wire and the one on the right go together (19) and the one on the left goes to the field (F)

Is this for a bug or Type 3?

Is this any help?

if not go to
http://www.vintagebus.com/

and try and find the right one

too small obviously

It was 1960-61 Austrlian