23. Phurnacite briquettes, manufactured by Coal Products Limited at Immingham Briquetting Works, Immingham, North East Lincolnshire, which–
(a)comprise anthracite duff (as to approximately 65 to 85 per cent of the total weight), petroleum coke (as to approximately 20 per cent of the total weight) and a molasses and phosphoric acid binder (as to the remaining weight);
(b)were manufactured from those constituents by a process involving roll-pressing and heat treatment at about 300°C;
(c)are ovoid-shaped briquettes with two parallel indented lines running longitudinally around the briquette;
(d)have an average weight of 40 grammes per briquette; and
(e)have a sulphur content not exceeding 1.5 per cent of the total weight.