39.  Supacite briquettes, manufactured by Maxibrite Limited, Llantrisant, Rhondda Cynon Taff, which—

(a)comprise anthracite fines (as to approximately 84 per cent of the total weight), petroleum coke (as to approximately 12 per cent of the total weight) and a starch binder (as to the remaining weight);

(b)were manufactured from those constituents by a process involving roll-pressing and heat treatment at 240°C;

(c)are unmarked ovoids;

(d)have an average weight of 45 grammes per briquette; and

(e)have a sulphur content not exceeding 2 per cent of the total weight.