As others have said there is 3 versions of the RCD-510
RCD-510
RCD-510 with rear view camera input
RCD-510 with DAB.
The DAB versions easy to spot it has a DAB button on the front panel. 
And a dab aerial connection on the back too, for anyone considering upgrading for DAB you might need some sort of aerial wire.
Yes. I did not mension this as the original thread poster has a RCD-310DAB unit so i expect would have the extra rear window conections and interface box from the factory so should be a simple plug and play upgrade for them just not everyone else.