10. Black Diamond Gem briquettes, manufactured by Coal Products Limited at Immingham Briquetting Works, Immingham, North East Lincolnshire, which—
(a)comprise anthracite duff (as to approximately 20 to 30% of the total weight), petroleum coke (as to approximately 40 to 45% of the total weight), bituminous coal (as to approximately 12 to 22% of the total weight) and 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 pillow-shaped briquettes marked with two parallel indented lines running latitudinally around the briquette;
(d)have an average weight of 160 grams; and
(e)have a sulphur content not exceeding 1.5% of the total weight.