Well I sure have been getting my share of old wiring lately. Came across this one last week. All of the exterior walls (masonary)contain conduit which contains one insulated black wire and one bare copper wire for the neutral! The conduit is all intact up to each box, and where it connects to the interior walls there is a feed of armored cable coming down from the VERY LOW ATTIC. There is even sone conduit on some interior walls, like to the furnace. However there is no way to get to the J-boxes where the Armored cable feeds in many cases. Ductwork was added in the attic making many areas totally inaccessable. I pulled in new insulated wires where I could but there is still a fair amt of bare copper being used as a neutral. Of course the conduit is carrying neutral current as well as the jacket on the armored cable that is solidly bonded to the J boxes and pipe.
I have never seen this done before, it was obviously done at construction in the late forties. Was this ever legal?
My concern is an open neutral somewhere between the conduit and the panel on the armored cable causing overheated armor.
That stuff was used during the war because of material shortages, maybe some of it was left after the war. I've never seen that stuff in person, I only read it was quite common in Northern Germany where most houses mainly consist of straw... ugly! The only wartime wire I've ever seen is old conduit wire, looks like the standard cloth covered wire but at a closer look there is no cloth... only the most brittle rubber I've ever seen! There were such rubber wires with much older cloth wires in one and the same conduit, the rubber stuff crumbled the instant I touched it and the cloth wire was still like new. I think aluminum wire was also a deal during war because they needed the copper for ammunition. Supposedly they also used some weird iron alloy named "new silver" for stranded wire back then... it's extremely springy and a bear to work with. I once saw it on an old radio.