Tag Dr specialize in License Plate Restoration and Repaint.
Check out examples of their license plate restoration on their website.
They say:
The Tag Dr. can restore your license plates back to original quality. Even one of a kind tags that have holes, rust, and missing pieces can be repaired to displayable condition.
I have restored tags for classic automobiles, motorcycles, restored hot rods, personal license plate collections, birth year runs, tag toppers, embossed highway signs, and bicycles.