The cases would be most likely steel. There will be some aluminum in there, but not a lot. I would take them even if they didn't have aluminum. Easier to get 10 pounds of steel than 1 pound of aluminum, and you would get $0.80 for the 10 pounds vs. $0.50 for 1 pound of aluminum. If you find a buyer for the boards inside, there is more money, plus you get a nice handful of insulated wire. I don't get what a lot of people get for wire but it adds up. If you strip the wire, you can get even more and it doesn't take up a lot of space.