I've run into this one time before and I think I posted it here but don't remember the answer(s). While renovating a residence I found an armored cable that had a lead covering over the insulated wires (it's usually paper or a waxed cloth covering) . I'm sure the cable is very old but I'm not sure why it was used inside the residence. I'm also unsure of why it was manufactured with the lead lining. If anyone knows the answers please post it here. Thanks.