Also, I was in a band in the mid 70s with a slide guitarist who used Rotosound Top Tape flatwound guitar strings on both his Dobro and his Shaftesbury Les Paul.
Rotosound, Picato, Pyramid, GHS, La Bella, Fender, Gibson, Rickenbacker, and probably several others were all supplying flatwound bass and guitar strings in the 1970s.