The firm of Douglas & Co., of 7 South Street, London, E.C., sold zither banjos with their name etched on a small celluloid disc let into the peghead. (or embossed on the back of the peghead and on the heel)
Edward F Douglas was born in Scotland in 1832 and was recorded as a Music and Pianoforte seller in 1881. By 1911 he was widowed, a retired piano tuner and he died in 1915.
The inlay on the back of this instruments is similar to G. Houghton of Birmingham.
Douglas & Co