Well, not a number plate, but I saw this on a big Swedish transport truck-trailer at the Nuerbergring:
SSA ruoy no rac 1 alumroF a evah uoY !won revo evoM
Too bad you can't type in true mirror image, like in Through the Looking Glass.
Trice
1968 280SL US, signal red/bl leather, auto, kinder
Sarasota FL; Alsace France