Martyn (H.H.) & Co.

H. H. Martyn & Co. was a well-known firm of sculptors and carvers based in Cheltenham. Established in 1874, they finally closed just short of their centenary in 1971. It provided a service for architects and grew to employ more than a thousand people. It decorated the interiors of many famous ocean liners and during the First World War it diversified into aircraft production

The firm established a stained glass studio in 1919 and appointed Sidney Meteyard as designer, despite his continuing to work from his Birmingham base. It lasted barely 10 years but produced designs across the country.

Sources:
Stained Glass Window Makers of Birmingham School of Art by Roy Albutt (2013)
H. H. Martyn & Co. on Wikipedia