These stickers, one on each side of the license plate, have been on the rear lid shell (?) almost since the car was new. The reason is simple, the original reflectors in the rear bumperettes didn't (don't?) match the regulations and my father didn't want to drill holes in the bumper to mount bigger ones.
The sticker is ~11,5 cm in diameter and the letters are 1,6 cm in height. Well, the questions are related to the fact that they are in a rather bad shape already and that I need to take them off for the new, black paint: