Back in the 1960's, Cadillac used aluminum bumper ends on some models, however, I have no idea why. They are extremely rare today. I bought one at Carlisle from a guy that knew exactly what it was for $300, and put it on eBay, and sold it for just shy of $700. I haven't seen another since, and the one that I bought was back around 2012. They were originally casted, polished, and then chrome plated. Never understood why they went with the aluminum, when steel was so prevalent in bumpers, and the center sections were made of steel, just the ends were aluminum.