Wu shu's were definitely the most popular Chinese coins of all times. From the 1st century BC to the 6th century AD, those coins seemingly satisfied the monetary needs of the Chinese population. Since wu shu's did not bear the name of the ruler or of the era, they could be used throughout political changes: Every new dynasty could leave the coins of its forerunner in circulation. Hence wu shu coins remained almost unchanged over many centuries. For this reason they are often difficult to date. And even though the issue of wu shu's ceased in the 6th century, they sometimes emerged in circulation until the 19th century.