 In the year 175 BC, or the fifth year of Emperor Wen, the government of the Han dynasty set the weight of the Ban Liang cash coins at 4 "zhu".These cash coins typically have a diameter between 23 and 25 millimeters and they tend to have a weight of 3 grams or less.Some 4 "zhu" Ban Liang casb coins have an outer rim, while a far fewer number of this type of Ban Liang have both an outside rim as well as an inside rim located around the square centre hole.