Jaguar Heritage Certificate questions

On the Jaguar heritage certificate there are several items that I had questions on.

They are:
Original Distributor
Original Dealer
Registration Mark

Does anyone know what the distinction is between the Dealer and the Distributor as it pertains to the car or certificate?? I'm looking at a S1 coupe certificate that has the Distributor in Rome, Italy

What does the Registration Mark pertain to? This car has a Registration mark number (looks like an english license plate #) that states ( Issued by Coventry) immediately after the Reg mark number

Anyone have a clue what this means?

Thanks for the help!