Square footed spade coins (fangzubu) were introduced in the 5th century BC in the realm of the Han clan. They were soon widely accepted and used far beyond the borders of Han, however. The average weight of the fangzubu-coins lies between 5 and 6 grams. Additionally there were pieces of double weight. Although fangzubu was cast in diverse mints, their alloy, weight and size do not vary. Evidently fangzubu was cast by order of a single moneyer, trying to form a large contiguous currency area.