Can you crease it with your thumb nail? Lead is that soft. Wheel weights won't crease, they have tin in them and are harder. Back in the day of slow moving vehicles, like horse drawn wagons etc. babbit was used for bearings. Babbit melts like lead or pewter, but is too hard to crease, because like wheel weights, there is tin in it. Depending on where you are finding it, and the hardness would give you an idea if they were pouring bearings, (hard) or casting round ball bullets, (soft) or plumbers lead, also on the softer side, because once poured it was pounded to expand and seal the joint.