Wu Zhu
Wu Zhu is a type of Chinese cash coin produced from the Han dynasty in 118 BC when they replaced the earlier San Zhu cash coins, which had replaced the Ban Liang cash coins a year prior, until they themselves were replaced by the Kaiyuan Tongbao cash coins of the Tang dynasty in 621 AD. The name Wu Zhu literally means "five zhu", with a zhu being a measuring unit officially weighing about 4 grams; however, in reality the weights and sizes of Wu Zhu cash coins varied over the years. During the Han dynasty, a very large quantity of Wu Zhu coins were cast, and their production continued under subsequent dynasties until the Sui.
The production of Wu Zhu cash coins was briefly suspended by Wang Mang during the Xin dynasty, but after the reestablishment of the Han dynasty, the production of Wu Zhu cash coins resumed. They continued to be manufactured for another 500 years, long after the fall of the Eastern Han dynasty. Minting was definitively ended in 618 with the establishment of the Tang dynasty. Wu Zhu cash coins were cast from 118 BC to 618 AD, giving them a span of 736 years, which is the longest for any coin in human history.
History
Western Han dynasty
"Wu" means "five" and zhu was an ancient Chinese unit of weight equal to 100 grains of millet. A "five zhu" cash coin would weigh about 4 grams. Originally Ban Liang cash weighed 12 Zhu as a Liang was 24 Zhu, however over time the weight of Ban Liang cash coins gradually decreased so the Wu Zhu cash coins were introduced as a new standard unit under the reign of Emperor Emperor Wu. The introduction of the Wu Zhu also fixed the standard exchange between bronze coins and gold as 10,000 bronze Wu Zhu cash coins would be worth 1 Jin of gold.The first Wu Zhu cash coins had unfiled edges, but the second series issued under the reign of Emperor Wu were filed. In 118 BC the central government of the Han dynasty ordered both the Commanderies and the Principalities to cast Wu Zhu coins, so these Wu Zhu coins are referred to as coins which at most have a diameter 33.3 millimetres and a weight of 5.8 grams. A notable feature of Jun Guo Wu Zhu coins is that they have a rim around the square center hole of the reverse side. These rims were added to prevent people from scraping metal off the coins, which would reduce their value. Another notable feature of these early Wu Zhu coins is that they tend to have edges which are unfiled, making these cash coins have rough edges; they are notably also heavier than later cast Wu Zhu coins. In 115 BC Emperor Wu decreed that all Wu Zhu cash coins should be cast with a value of 5 cash coins. These coins are known as or because as they were filed, they gained "red" or "purple" edges that showed as the copper became visible. Another feature of these cash coins is that the "Wu" character tends to be composed of some rather straight lines.
Starting from the year 113 BC, the central government regained the exclusive authority to manufacture coinage. From this point Wu Zhu cash coins started being produced by the Three Offices of Shang Lin. These Wu Zhu coins had a nominal value of one coin as opposed to the Chi Ze Wu Zhus, which had an unrealistic nominal value of five. The majority of the Shang Lin San Guan Wu Zhus contain a raised line above the square center hole on the obverse side of the coin.
Under the reign of Emperor Xuan, which lasted from 73 BC until 49 BC, the Wu characters were small in size and notably written with slightly crooked strokes that didn't extend to the horizontal lines of the top and bottom ends. A number of these Western Han dynasty Wu Zhu cash coins also displayed dots, which represent "stars", and crescents, which represent the moon, on the interior rim of the coin as well as other symbols which were considered to be auspicious. These became some of the earliest examples of cash coins used as Chinese amulets and charms.
In the 123 years after 118 BCE, when Wu Zhu cash coins were initially introduced, over 28 billion coins were cast for circulation.
Xin dynasty
After Wang Mang had overthrown the Han dynasty with his own Xin dynasty, he wished to displace the Wu Zhu currency of the Western Han dynasty. This is believed to be part of his prejudice against the "Jin" radical in the character of this inscription, which was also a component part of the character Liu, the family name of the rulers of the House of Han— whose descendant Wang Mang had just dethroned. He introduced a number of currency reforms which met with varying degrees of success. The first reform, in AD 7, retained the Wu Zhu coin, but reintroduced two versions of knife money. During a later reform the Wu Zhu cash coins were completely abolished, and Wang Mang placed the death penalty on anyone who dared to circulate any Wu Zhu cash coins. However, as the new currency system introduced by Wang Mang was chaotic and confusing, Wu Zhu cash coins kept secretly circulating.Chengjia
The Iron Wu Zhus of Chengjia, which resemble the Western Han dynasty Wu Zhu coin, is attributed to Gongsun Shu, who rebelled in Sichuan in AD 25, and issued iron coins, two being equal to one Jian Wu Wu Zhu. These had the head of the zhu component rounded, typical of Eastern Han Wu Zhus. In AD 30, a ditty was sung by the youths of Sichuan: "The yellow bull! the white belly! Let Wu Zhu cash coins return". This ridiculed the tokens of Wang Mang and the iron coins of Gongsun Shu, which were withdrawn by the Eastern Han Emperor Guangwu in the 16th year of Jian Wu. The Emperor was advised that the foundation of the wealth of a country depends on a good political economy, which was found in the Wu Zhu coinage, and so reissued the Wu Zhu cash coins.Eastern Han dynasty
After the fall of the Xin dynasty, the production of Wu Zhu cash coins was resumed under Emperor Guangwu who reigned from the year 25 until 56 AD. Under the reign of the warlord Dong Zhuo, the capital of the Han dynasty was moved from Luoyang to the city of Chang'an. There, he ordered that the large Qin dynasty era bronze statues dating back to the reign of Emperor Qin Shi Huang be melted down to make small cash coins. A large quantity of these Wu Zhu coins were so small that they were commonly referred to as "goose eye coins" or "chicken eye coins" by the people. As these cash coins were so diminutive in size, only left half of the wu Chinese character and the right half of the Chinese character fit on these coins. It is also pivotal to clarify that these cash coins are not "chiselled rim coins", where regular-size Wu Zhu cash coins had their insides cut out so as to form two separate cash coins. Goose eye/chicken eye coins were actually cast in this diminutive manner, as evidenced by the remnants of the metal sprue from the casting process on their rim's five o'clock position.The Three Kingdoms
The Three Kingdoms period was an era in Chinese history that lasted from 220 until 280 and was characterised by a period of disunity following the collapse of the Eastern Han dynasty. The Kingdom of Shu Han was founded after Liu Bei seized control of the city of Chengdu. Immediately after the city was taken, Liu Bei had discovered that the treasury was completely empty, which meant that he didn't have the funds for his military expenses. This was paired with a severe shortage of copper, this severe lack of copper was so bad that it is said that in order to manufacture cash coins even the hooks which were used to hang bed curtains were melted as the government desperately needed the metal. To cover the state's expenses, Liu Bei ordered the creation of cash coins which had a nominal value or one hundred regular cash coins. Unlike the earlier coinage of the Xin dynasty, which disastrously failed due to the extreme disparity between the nominal and intrinsic values, the coins of the Kingdom of Shu Han weren't as badly received. These Wu Zhu cash coins produced by Dong Zhuo only weighed around a single gram, previously a cycle plagued Chinese governments trying to set of a fiat coinage system where first the government issued new cash coins, then the government would set values, usually the people don't accept these set values, and then finally the currency doesn't trade which causes inflation to set in and counterfeiting becomes a prominent problem. Zhi Bai Wu Zhus are usually divided into "thin" and "thick" types depending on the thickness of the cash coin. It is also believed that the Kingdom of Shu Han under the reign of Liu Bei cast a variant of the Wu Zhu cash coin which had a rim around the square hole that is 21.7 millimetres in diameter and has a weight of around 2.3 grams. Due to this association, they are known as the cash coins, but due to later archeological findings this isn't taken with absolute certainty.In the Kingdom of Cao Wei which was established by Cao Cao in 220 it is believed that only Wu Zhu coins were cast. Moulds have been found dating to this period and it is confirmed that Wu Zhu cash coins were cast from the first year of the Taihe period until the second year of Xianxi period.