I believe Rotosounds were the first Nickel plated, for sure first round wounds. And they were nickel plated... Interested myself.
I do know that non stainless steel were used first, back in the day strings could/would rust. The Cobalt strings are kinda a throwback to a non stainless steel. Then Stainless steel, then nickel...
Be Groovy :cool:
Remember folks at the end of it all this is about having fun and entertainment :p