The Sealmaster range of door and window seals won a Design Council Award in 1968. Used to seal against radioactivity, draughts and dust, seals were installed in buildings such as hotels and laboratories, and were used to draughtproof the doors of St Helen's Church, Bishopsgate. The seals at that time were not available to the general public due to their complex installation process.

The original idea for this type of seal was conceived by Australian, R. F. Macdonald who travelled to London to sell his idea in February 1963. He approached Dixon International Projects Limited, who specialised in developing inventions either by arranging production under licence or by providing finance and manufacturing capabilities. In this case the business' subsidiary, Sealmaster Limited, developed and manufactured a range of seals, some based on Mr Macdonald's idea, and others of entirely new design. The original materials, aluminium and rubber, did not perform well so after some research, a hightensile heat-treated aluminium alloy was chosen for the extruded sections. Neoprene was selected to replace the rubber and the Du Pont company advised on the use of different grades of Neoprene for different kinds of seal.

Bernard Dixon, a financier and inventor, and E. Leslie Brooks were also involved in the product development and design detailing of this product.