That particular "BARLING'S MAKE" stamp is pretty early. I'd need to see good photographs of the bit and slot, but it could date anywhere from about 1939 to 1947, based on what I can see. Since it's stamped EL, no earlier than 1938-9. Give it some very careful TLC. I'd use micromesh pads to remove the oxidation and polish the stem, but chances are the oxidation goes pretty deep, so you may lose some of the flush level between the stem and the shank. It should provide you with an excellent smoke once you have cleaned it up inside and out.
Congrats!