I have split this topic off from Tony's to avoid future confusion.
Your bike would have originally had an electrical system. Had it been fitted with carbide lighting, it would have a 'plain' timing cover with no aperture for the BTH PA series dynamo. You do have an interesting adapter fitted to the opening for the dynamo, to use some sort of smaller dynamo of unknown make.
The accumulator/battery carrier is the original. It is missing the straps that clamp the battery. Could you take a photograph of the back side, as eventually I will need to make one for my F28.
The holes in the number plate could be either for a acetylene lamp or a small electric tail lamp. The factory offered BTH headlamps at this time, so I suppose the electric tail lamp would also be BTH. But electric lighting (or acetylene) was very much a customer preference at this time. They would just order the basic electric model from the factory and shop around and have the dealer install the lamps.