Hi Justin,
Well those Rover ID plates are a bit of a pain as they are graphically screen printed on to the Ally plate, thus it is rather impossible to refurbish unless you are in the graphics arts game and have facilities to the equipment required to do this.
I guess the best thing you can do is lightly wet and dry it until you've got a nice brushed looking finish and it will only show the Model and serial numbers which effectively is the only info on the plate apart from the makers name and address which we all know.
After you've done that use a good clear enamel and seal it without getting any finger prints on it prior to spraying and this way it will look good for years.
The old brass ones are a totally different kettle of fish to deal with but certainly look much better after refinished.
Cheers,
BB.
