Technical Flathead 12V Regulator connections

Bought a 12Volt generator for my flathead and i dont have a clue how to connect the regulator.

The regulator is marked L - BAT - F

The F is Connected to Field on the generator.
The Connection under the regulator goes to Armature.

I guess the BAT is the one who charges the battery?
But were does the L go?

 

I think you need to find an elderly mechanic with experience in northern Europe, or perhaps a catalog or manual from the electrical company that made the regulator.
What you have I think is a mid-1930's Ford generator, made originally as a 6V and originally unregulated...it had originally only a cutout meant to disconnect it from battery when engine was switched off. It had 3 brushes (does your converted one still have 3??) and one of those set the amperage, which was not otherwise regulated.
Your device looks like it was designed to fit on the many older generators that carried a cutout on top...it is entirely non-Ford in origin though.

 

It had me guessing. Never seen anything like that. especially for a 12V system.