The plate was purchased as a blank plate.
The plate has the solenoid for switching on the charging for the auxiliary batteries. This is controlled from inside the cab.
It is also where the control cable from inside the cab is terminated, and supplied 12v ignition switched power to the radios in the cab.
Everything is fused.
The control cable also includes switch signals for the driving lights, roof lighter and additional reverse lights. (still to be installed).