That's something I wonder about too. As long as they're authentic, isn't it better to have legible ones than rusty ones?
At least in CA there's apparently a law prohibiting restorations or reproductions.
But realistically, as long as it's a valid number and isn't duplicated (which they can easily check), what's the problem with either a restored or reproduced plate?
Several years ago I bought NOS original 1928 plates for my car. Gorgeous. They passed DMV with flying colors, naturally. But over the course of just a few years the old paint deteriorated something terrible. They became downright ugly, and no longer complemented the appearance of the car. I considered sending them out for restoration, but then they'd be illegal. So I went another route: I ordered reproductions with my number. Yeah, technically they're illegal, but who would ever know? If a policeman ever stops me they'll run the number and find it's valid. If for some wildly implausible reason a cop is savvy enough to cite me because it looks too perfect for a 1928, I still have my 100% original and 100% legal plates hanging on the wall of my garage. They could go right back on the car if I were forced to. But if I get them restored, there's no way to unrestore them....
The repros look terrific, by the way.
As a sidebar, I think that from the DMV's standpoint the bigger fear on repros is that someone orders totally conventional plates, then has repros made with the modern number and uses them as if they were YOM plates, without paying the YOM fees. It sure would be easy to do: get new standard plates, don't put the stickers on, order repros, and in 1 week you have 1928 or whatever year you want plates with the brand-new number. I'm sure that 99.9% of the time if someone were stopped, the cop would simply run the number and not think twice about whether it's a valid format for 1928, or whether it carries an official YOM certification. But that is really stretching the law; at least my repros are exact copies of originals and have the same original number.