10. Briteheat briquettes, manufactured by Coal Products Limited at Immingham Briquetting Works, North East Lincolnshire, which—
(a)comprise anthracite (as to approximately 60 to 85% of the total weight), petroleum coke (up to approximately 30% of the total weight), bituminous coal (up to approximately 15% 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 cushion-shaped briquettes with an indented line running longitudinally around the briquette and have an average weight of 30 grams; and
(d)have a sulphur content not exceeding 2% of the total weight.