Mother coin

Before modern industrial patterns were introduced into almost all fields of production, coin mints can be considered to be an outstanding example of an early form of mass production of attempting to create identical objects, or those as standardised and as similar to each other as possible.[1] Therefore, it wasn't only just the technological knowledge and the techniques that were applied which mattered, but also the general organisation and especially the division of labour that were crucially regarded of being of paramount importance to the assessment of both the efficiency and quality of the work of coin mints.[1] It wasn't until the Song dynasty period that contemporary sources started to actively record the works of coin mints to give insights into these early instances of mass production.[8][1]

The Song dynasty period saw an especially high demand for cash coins leading to not only bronze cash coins but also iron cash coins being mass produced for the market.[1] During this period government operated coin mints were generally divided into 2 types, namely bronze cash coin mints and iron cash coins mints.[1] However, this division wasn't absolute and at times bronze cash coin mints would produce iron cash coins.[1] During the Northern Song dynasty period a scarce number of sources started providing written evidence for both the usage of the "sand casting method" (翻砂法) and the application of mother coins to this process.[1][9] The Song huiyao jigao (宋會要輯稿) provides the earliest known evidence for the application of mother coins into the production process of cash coins.[1][10]

The History of Song records that during the year Daguan 1 (1107) that the emperor of the Song dynasty would distribute both "cash coin samples" (錢式) and mother coins to all cash coin producing circuits.[11][1] Later the Rhapsody of the Great Smelting (大冶賦) published in the year 1210 records a poem that completely details the cash coin manufacturing process detailing its use of mother coins.[1] Both of these works explicitly mentioning how mother coins were applied in the sand casting method at the time and how they were used to form the patterns for cash coins in the sand moulds.[1]

Notably, the Rhapsody of the Great Smelting records the sentence "scrubbing the cash coins with grain chaff", which wouldn't be mentioned again in the historical records 689 years later in the Qing dynasty period 1899 book A Survey of Casting Coins (鑄錢述略), which indicated the long continued usage of this method.[1]

There were two different types of mother coins, namely engraved mother coins and cast mother ones.[1] Engraved mother coins were typically made of materials such as wood, tin, copper, or ivory, while cast mother coins were exclusively made of copper or tin.[1][12] The usage of mother coins varied in different dynasties and time periods, while the changes in the rest of the sand casting technique of cash coin production itself were rather marginal.[1]

A Qianlong Tongbao (乾隆通寶) ancestor coin produced during the Qing dynasty, on display at the National Museum of China.

Ancestor coins (traditional Chinese: 祖錢; simplified Chinese: 祖钱; pinyin: zǔ qián), also known as engraved mother coins (Chinese: 雕母; pinyin: diāo mǔ), master cash,[1] or progenitor coins,[2] were introduced around 1730 in middle of the eighteenth century to improve the quality control of mother coins,[14] these ancestor coins were used to cast more mother coins and from a single ancestor thousands of mother coins could be cast. The production process of making mother coins with ancestor coins was the same as it was for the casting of circulation coins from mother coins, however these coins were usually only produced for a new reign title, when preparing to cast new cash coins with new inscriptions for a recently ascended emperor, a mint would first engrave an ancestor coin out of fine brass which would form the basis for mother coins. The introduction of ancestor coins under the Manchu Qing dynasty lead to all mints having more consistently produced coinages and smaller variations between the coins produced by separate mints in both inscription (or legend) as well as in quality.[15][16][17][18][19][20]

• On November 30, 2014, a Qixiang Tongbao (祺祥重寶) engraved mother coin was sold at an auction in the city of Beijing for $129,843 (which at the time was worth 808,500 yuan).[18]

A Thánh Tống Nguyên Bảo (聖宋元寶) which was cast by using a circulating cash coin as a mother coin.

Iutsushi (Japanese: 鋳写し) is a Japanese term that could be translated as "to cast a copy from", this refers to a technique where regular circulating cash coins were used as mother coins, this was a very common practice in Japan until the seventeenth century and mostly Chinese cash coins from the Song and Ming dynasties were used. Outside of Japan this technique was also largely used to produce counterfeit currency by illegal Chinese and private Vietnamese mints, as the cash coins produced by using the Iutsushi technique were less crisp than their mother coins, often have smooth reverses, and the fact that these coins shrunk after metal had cooled down, Iutsushi coins are also diminutive in size compared to the original circulating coins and the inscriptions are also inferior in quality as they display more softer and quite blurry. For these reasons the cash coins produced using this technique were among the cash coins known as Bitasen (鐚銭) or bad metal coins in Japan.

Due to Iutsushi, it is often very hard to distinguish Japanese Bitasen from Chinese counterfeit cash coins as well as privately produced cash coins from Vietnam as many of these used the same inscriptions; it is not uncommon for there to be large variations in both the quality and metal content of original coins that have been heavily circulated.[21][22][23][24]