From the late 1800s to the 1920s, self contained 32v lighting systems (run by a small generator) were installed using bare iron wire. The wire was in the region of 1/4″-1/2″ diameter, with no insulation at all. Very unlikely to be encountered today.

In Conclusion

While we were doing the research to proofe this article we found a few manufacturers, admittedly in India and china, still selling brand new Vulcanised Rubber, and Aluminium cable for use in the home.

As well as Copper Clad Aluminium cables starting to be used again (in a fight against the high price of copper) as speaker wire in cars, of all places, in the United States.