I saw today what appears to be non metallic wiring from the 50’s - three wires with a ground (bare copper) wrapped around the wiring jacket. Similar to the way you do wiring with BX wiring. The jacket was silver but most seemed to have faded away leaving it black.
I am not at a computer that I can upload a picture but can at a later date.
Question - any concerns here? My guess is the plugs and switches are ungrounded.
He is an image (also posted below)