1939 quadruple rate cover sent registered air mail to England with a 5/- and a 4d cancelled BLANTYRE 8 DEC 39. This 5/4d rate correctly pays a letter of between 1½ and 2oz, the air mail rate being 1/3d per ½oz. and 4d registration. This rate came into effect on 4 September 1939. Uncommon.