Can you show a pic of a royal with one?I believe it was an option, possibly only on 300's. You don't see them on many cars, 1970's had them too. Not sure about '71. My '71 New Yorker has a full width rubber strip on both bumpers, which I've only ever seen on a few other cars. Then there are the huge bumper protectors that were optional on '71 Newport Royals. Those are really rare.
Found one!Can you show a pic of a royal with one?