Earlier quoted context omitted.
The entire skin. Quite thick - not really wearable.
It actually might not be illegal. I was on safari last year and I was told you could buy a license to hunt leopards, just they are very expensive. You can also hunt lions and other big game.
Wild Leopard is a CITES Appendix I species, meaning that it's pretty much illegal to trade in or to move across borders. It's possible to do it legally, but in order for that to be the case your family would have needed a special export permit from where they hunted it, and they would have had to get a similar permit from the Fish and Wildlife Service to bring it back into the US - and this is quite difficult.
If they can prove that it was bred in captivity, then it only requires a FWS import permit (since captive Leopards are CITES Appendix II), which is reasonably easy to get.