In 1595, kin-za started when Ieyasu TOKUGAWA ordered the metalworker Mitsutsugu GOTO in Kyoto to cast koban (former Japanese oval gold coin) in Edo. After the establishment of the Edo bakufu, kin-za was under the control of kanjo bugyo (commissioner of finance) and an official residence was located in Hongoku-cho in Edo.
After the establishment of kin-za, the Goto family only worked for appraising and approving of gold coins as Gokin Aratame-yaku (inspector of gold coins) at the official residence in Hongoku-cho and actual casting was performed by workmen called koban-shi. Koban-shi were collectively called koban za and they had facilities around the official residence of kin-za in Hongoku-cho where the head family of the Goto family lived and they were under the control of the family. Therefore, the head family of the Goto family who inherited Gokin Aratame-yaku was also especially called Ooban za in the meaning of the manager of koban za (koban-shi workmen). However, in order to prevent tightening of control and decentralization of koban-shi, in 1698 casting facilities outside the residence were abolished and casting facilities were located on the grounds of the official residence of kin-za (the residence of the head family of the Goto family) only where casting of gold coins was performed thereafter. Furthermore, after 1765, the operation of casting small amounts of copper coins was shared by kin-za and gin-za (an organization in charge of casting and appraising of silver during the Edo period) (see the article of gin-za [history]). In addition, the head family of the Goto family was ruined in connection with misconduct in duties in 1810, and the branch family who was ordered to be the successor to Gokin Aratame-yaku was also ruined in connection with criticism of bakufu in 1845. Then the descendants of the former head family who had been permitted to return to Edo were allowed to restore the family and returned to Gokin Aratame-yaku to control kin-za until the end of the Edo period.
At first, in addition to Edo, kin-za was also installed in Sunpu, Kyoto and Sado (later in Kofu), but it was integrated in Edo later. However, kin-za located in Anekoji Kurumaya-cho, Kyoto, where casting was stopped in 1791, was not abolished and gold working for official business of the Imperial Palace and control of gold workmen in Kamigata (Kyoto and Osaka area) and so on were performed under the control of the Goto family until the end of the Edo period. In addition, casting was performed in kin-za in Sado and Kofu until Bunsei era.
Officially, they were abolished when kin-za and gin-za in Edo were occupied by the government army in May 9, 1868. However, the requisitioned kin-za was actually under the regulation of Kaheishi (currency office) of a new government and cast gold coins to be used by the new government until February of the following year to apply the money to payment of military expenditure of the Meiji Government. However, because the fact that kin-za was casting inferior gold coins in violation of kaizei-yakusho (revised agreement on trade attached to the Ansei Five-Power Treaties) was revealed, it met with protests by many foreign countries and kin-za was abolished because the Meiji Government decided full switchover to dajokansatsu (government note) and construction of the mint bureau.
There is an avenue called Kinza-dori avenue around the Bank of Japan in present Chuo Ward, Tokyo (Tokyo Prefecture), which is the site where kin-za previously stood. Also, in Shizuoka City, the place where koban (former Japanese oval gold coin) was casted still remains as a town name of Kinza-machi. Similarly, there is a town name of Zeniza-machi.
After 1765, kin-za and zin-za (see the article of gin-za [history]) also were in charge of the operation of casting coins and as a result gin-za which had been a contracting business by private merchants was under the regulation of kin-za. Especially, Tenpo-tsuho issued following the advice of Mitsunori GOTO who was Gokin Aratame-yaku was casted at the initiative of kin-za. Kao (written seal mark) of Mitsutsugu Shosaburo GOTO of kin-za was cast on the reverse side of Tenpo-tsuho.
Method of casting koban
At first, refining of bullion was carried out and monitored in the presence of Goto-tedai (clerks of the GOTO family). Mountain golds purchased from gold mines, old gold coins and imported gold ingots were melted, and then salt and sulfur were added thereto to react with silver included in gold and then refine to produce a certain carat of pure gold. The carat was amended compared with a model gold using a touchstone. Then pure gold and hanafuri-gin (pure silver) were weighed, combined so as to achieve a specific carat, and melted in a melting pot to produce sao-gane.
Kin-za nin (people in kin-za) received these bullions, which were cut off in a given weight and beaten out in a form of koban. After the surface of koban was chiseled and weighing and inspection were performed, hallmarks of toryo (master) and zanin (hereditary officers of kin-za and gin-za in the Edo period) were punched and koban were handed over to Goto-tedai. Koban were further inspected and hallmark of paulownia with a fan-shaped frame and hallmark of its face value were punched on koban, then koban were returned to kin-za nin.
For finishing, enhancement of the color was performed by applying agent such as salt, niter, chalcanthite, melanterite or kunroku (a sort of resin) to koban and warming koban over a flame to make gold color complete. Koban that had passed final inspection were packed by the hundred ryo (currency unit) to make tsutsumi-kingin (a certain amount of gold coins and silver coins packed and sealed in a piece of Japanese paper) and delivered to kanjosho (financial office in the Edo bakufu).