I recently went to the scrap yard with a bunch of metals. I took quite a bit of old HVAC ducting from my 1947 home. I thought the metal used was tin but the scrap guy seemed to think it was aluminum and gave me the aluminum price. He scratched it with a knife. I thought they used tin back in the day to make ducting, but maybe I'm wrong. The metal was very pliable and had a yellowish/silver hue to it. Was he right?
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