wayne1956 
Most of these are die cast zinc plated with brass. Die cast zinc is what alot of people call "pot metal" (it's actually a series of alloys called Zamak or Mazak) . The easy way to tell them from aluminum is that they will be heavy and aluminum is light. Also, die cast zinc gets a grayish color to it as it oxidizes. If you know what color an unpainted matchbox car is then you know what color zinc is.
Getting a fair price for zinc from a yard is hard to do as almost nobody knows what it is and they can get away with screwing you. Spot price for zinc right now is about $0.94 lb. I have been putting it in barrels and when I accumulate a ton or so of this I'll go shopping it.
Usually if you can fill a gaylord with anything you can negotiate for a fair price.
There is a huge amount of stuff made out of this but many people can't recognize it. If you've got cast alumunum that seems too heavy to be aluminum it's probably zinc.
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