I have a '56 Victoria (not a CV) and I don't know about the '55s but all the side moldings on mine are stainless. I don't know about the Crown, or tiara.
The plated pieces on mine are bumpers & guards, grille sections, parklamp housings & extensions, door handles, vent window frames, hood ornament, part of the side window frames, backup light housings and badges/nameplates. Not sure but the tail light housings might be plated too.
Ron