R49 Stock.

'M.G In' = "Motor Generator In" i.e Motor Generator running.
This was a non-illuminated flag indicator, if the M.G didn't run the flag dropped down inside the box and then nothing was shown. There is therefore no 'current lamp' as you call it.

Yes, there was a Guard on the rear of the train but there was no 'door lamp' for the driver. The only indication the driver had that the doors were initially closed was the bell signal ringing in his ears! (mounted just behind his head). While driving along, the driver had no indication that the doors were remaining closed therefore- just the Guard looking at his indications on the rear of the train.