i believe the trunk star is held on by mounting pegs but the other emblems are adhesive. (at least on the later models)
my 190E was repainted by the previous owner and i suppose he left the emblems off. there are no holes where they should be. so i would guess its adhesive.
i do want to buy a new 190E emblem though. the bareness bugs me. i cant seem to find anywhere that sells the 2.3 emblem though.