McVitie Weston valve collection, BTH valve, type N.R. 7X
BTH valve, type N.R. 7X, etched H, (RMW/B83 - McVitie Weston number), by British Thomson-Houston Company Limited.
BTH valve, type N.R. 7X, etched H, (RMW/B83 - McVitie Weston number), by British Thomson-Houston Company Limited.