It's the stamping, to me one side is much more crisp than the other, I've only seen them once, but someone else told me they thought the same thing....
I had a set about 15 years ago. As mentioned the beltlines weren't as sharp and didn't match up at the door edge right, the bends at the front and rear weren't sharp like Ford pieces, they were kind of rounded. Useless for anything more than making patch panels. I ended up taking them of and getting a pair of NOS quarters.
