7. Briteflame briquettes, manufactured by Maxibrite Limited at Mwyndy Industrial Estate, Llantrisant, Rhondda Cynon Taff, which—
(a)comprise 10 to 15 per cent bituminous coal, 10 to 15 per cent petroleum coke, 70 to 80 per cent anthracite duff and starch binder (as to the remaining weight);
(b)were manufactured from those constituents by a process involving roll-pressing and heat treatment at about 260o degrees C;
(c)are unmarked pillow-shaped briquettes and have an average weight of 140 grammes per briquette; and
(d)have a sulphur content not exceeding 1.9 per cent sulphur on a dry basis.