The so-called knife or key coin joins two traditional Chinese coins: The upper part is formed like a round coin, while the lower part imitates an ancient knife coin. The inscription on the coin says "one knife worth 5000," referring to 5000 round copper coins (wu shu). At that time, 5000 wu shu approximated 60 grams of gold. This knife coin thus had an enormous purchasing power. This was made clear to anybody by the fact that the writing was made in gold. The use of precious metals, especially gold, was very scarce in Ancient China's currency system.