66 Barracuda rear bumper pads or guards?

I’ve never seen those before. They look like something they would had put on for shipping the cars via rail or truck back in the day since that part of the number sticks out the most.
All the ones I have seen were vertical front and rear.
I may be wrong but I’ve stripped more of these cars (1966) than I want to admit and never seen this style before.
Just my two cents.