58. Multiheat briquettes, manufactured by Coal Products Limited at Immingham Briquetting Works, Immingham, North East Lincolnshire, which—
(a)comprise anthracite (as to approximately 60 to 80% of the total weight), petroleum coke (as to approximately 10 to 30% 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 unmarked pillow-shaped briquettes;
(d)have average weights of either 55 or 80 grams; and
(e)have a sulphur content not exceeding 2% of the total weight.