I also believe that all Hudson wiring is copper and not steel. I replaced my '50 C8 harnesses and they were all copper. I cannot believe anyone would use steel wiring for much of anything. Yes, it may look like steel due to the tinning, but steel wire would have so much internal resistance it would create significant heating, especially with 6V.
I wanted to add a bit more to this discussion. Here are some comments concerning the electrical conductivity of copper vs. steel. As noted, it would take significantly more steel, as the diameter of the wire, to carry the necessary current for even an older automobile than it would copper, i.e. it would not make any sense to use steel as a wiring material. This would even be more so with 6V vs. 12V. This should put to bed any further thinking that Hudson used steel for its wiring.
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https://www.quora.com/How-much-more-conductive-is-copper-than-steel?share=1