36. Sovereign briquettes, manufactured by Monckton Coke & Chemical Company Limited at Royston, near Barnsley, South Yorkshire, which—
(a)comprise anthracite (as to approximately 75% of the total weight), coal and reactive coke (as to approximately 21% of the total weight) and cold-setting resin binder (as to the remaining weight);
(b)were manufactured from those constituents by a process involving extrusion;
(c)are unmarked hexagonal briquettes;
(d)have an average weight of 130 grams per briquette; and
(e)have a sulphur content not exceeding 2% of the total weight.