 In the year 182 BC, or the sixth year of Empress Lü, the government of the Han dynasty began cast Ban Liang cash coins with a weight of 2.4 "zhu".These cash coins had a diameter that was only about 20 millimeters, and they were distinguished by a large square centre hole.Because in reality they were only worth one-fifth of an earlier Ban Liang coin, they are usually referred to as "5 parts Ban Liang cash coins" (五分半兩錢).