My grandfather in Philly had a Schoemacher upright(20's vintage) that is now at my sisters house.It has electro-plated gold strings.One broke in the high treble when I was an apprentice(this was in 1980 when we still used that word)..I showed it to my teacher and he said yes indeed it was electroplated gold and if I hadn't been overpulling the upper treble too much it probably wouldn't have broken.The bass strings are copper wound.
This PTG archive page provided courtesy of Moy Piano Service, LLC