Something to be very careful about when using or buying "lead" clip on wheel weights that have been collected in the past 4 or 5 years. I can buy them from a local scrap yard and
I have found that a lot of them are plastic coated metal or zinc or steel. The look almost identical to the old style real lead alloyed wheel weights but are a real pain to sort out. In fact unless you can
cut them in half you really won't know what they are made of. Usually, when I buy a bucket of clip-on wheel weights (not the the stick on type) about half of them are plastic coated zinc or steel.
Some of the plastic coated type have specific markings on them but the markings are pretty small and difficult to read.
From EPA Lead is a component of many existing wheel weights, though alternatives such as steel, zinc alloy and plastic-metal composite are now widely available, and according to information received by EPA, lead wheel weights are no longer used on new vehicles in the United States