I was going to mention same thing - possibly an SE cable? The bare stranded conductor would be concentric around the insulated conductor.Is the stranded insulated? Could be some old SE cable for a 120V service but that would depend on what gauge the conductors are. People do recycle old junk to save a penny & some depression era people do not like to waste anything.
I must say that all of those I ever recall seeing had a stranded insulated conductor instead of solid.Not uncommon on the 30 amp 120 volt services installed during the early 1930's as part of the new deal. There are still a few in use in unincorporated areas around here.