I found this mystery wire while changing out a plug In my home. It doesn't look like anything I've ever seen. I can't identify it by memory or google. I'm curious what it is commonly used for. Was it ever acceptable as house wiring in the United states?
The wire turned out to be a cable with three conductors. The insulation was melted almost 3/8ths of inch up under the white sheath. the receptacle was indeed spliced 6 inches inside the wall. I removed the spliced section and remounted the box at 40 inches for ADA compliance. Thanks to everyone who participated.