 By analogy with the "wai", this unclear character has been read as " nei" () or "zhong" ().The round coin, the precursor of the familiar cash coin, circulated in both the spade and knife money areas in the Zhou period, from around 350 BC.Apart from two small and presumably late coins from the State of Qin, coins from the spade money area have a round hole and refer to the "jin" and "liang" units.