I've always been told that from a distance you can't tell if a plate is legal or not just because it's pressed, obviously different fonts are different.
I drove around with illegal pressed plates for quite some time, the only time I ever got pulled up on them was due to the fact that an error on the Police system showed my car as uninsured when it was in fact insured. I proved it by the roadside, but when they went over my car with a fine tooth comb they saw the plates and gave me the ticket which means you have seven days to replace them. (I also didn't have a front plate at the time, schoolboy error)
Copper was alright enough about it, wasn't any attitude from him.
At the end of the day, generally, if you don't drive like an ass and draw attention to yourself you don't get pulled over.