Advertising: Cooper's Powder Dip The Only Reliable Preventive Of Blow Fly c1920s. Sign, enamel on metal, 67 x 51 cm. 'By appointment to H.M. The King. Patent Enamel Co. Ltd. B'ham & London.', William Cooper (1813-1885) was a British veterinary surgeon, agriculturalist and industrialist who specialised in the manufacture of agricultural insecticides for livestock. He is credited with developing the first successful sheep dip, Cooper's Dip, in 1852. The company is still in operation and the product was widely used in Australia.