It essentially ends with RH and RHW. Rubber, or synthetic rubber, insulated with an outer covering that was commonly a cotton weave impregnated with bituminous compounds. At the stripped end, the cotton would fray, hence, "rag".
Re: Ragwire#20650 01/18/0306:05 AM01/18/0306:05 AM
Seems to be exactly what was used in Austria for any type of wiring up until the mid-1950ies. Single wires, 1mm2 tinned copper, either directly buried in plaster /laying loose on the lathes in plaster and lathe ceilings, or in conduit. All a brownish-black color, makes for stinky and black fingers in any rewire (half of the house I live in is wired with that stuff and I replaced lots of it). Should be fused 6A, in most cases overfused up to 16A, typically 10A. Connections either twisted and taped, or conductors looped around a short screw and secured with nut and washer. One of those screw-and-nut connections started arcing shortly after we moved into our new appartment.