Greg, "old" romex. Each of the two wires are rubber coated and the outer jacket is weaved string which is cotton I do believe. I do believe but not certain that each rubber coated wire is also wrapped in the cotton? Weaved jacket but not certain
I am trying to remember the real old Romex. I grew up with the kind that had TW insulation, maybe a ground, maybe not and the shiny silver painted woven jacket. I may still have a piece that I cut out of this 1963 house but it is newer than the oldest I have seen.