The metal is smooth, but not shiny. It is super bendable. As soon as I realized what it was, I stopped handling it and washed my hands.
Lead is heavy, but seems such an odd choice for a weight in a consumer device. It must have been cheaper or even free.
It had a strip of double stick tape under it.
Ok yeah so that sounds like a mounting bracket for the battery itself. That’s normal, probably not lead.
Genuine Apple batteries will have a pull tab for safely removing the battery, this appears to be a less sexy version of that.