some of the old dozer tracks are made of some type of non magnetic alloy,,,,i have heard it called manganese but i am not sure if that is right or not ...i have not seen any of that type for a long time but they are still out there.....what ever type of metal it is i know our local yards would not buy it....id say now that i no how to use the internet i could probably find a buyer.. a few years ago i had an awful time getting rid of a set of them