G6ZW 1950 England

Van Zwanenberg Exp. Labs, London.
A little faded, but the QSO was with G3CMY in 1950, and the "Exp Labs" has been struck through in pen.
If you look, this is a 1930's QSL (with a George VI stamp on the rear) No cancellation date, but will be in the late 1936-1939 period)

G4UZN Collection