Keicho Oban (慶長大判)
Keicho Oban is a large-sized old Japanese gold coin issued in the early Edo period, from 1601 more specifically, and this can be classified into several varieties according to writings in ink, karat (gold measurement), timing of issuance, and so on. It is said that Keicho Oban was issued at the same time that the currency system of the Keicho era was established; however, its details are unknown and it is not yet laid out as a reliable fact.
Keicho Oban, Keicho Koban (small-sized coin), Keicho Ichibuban, Keicho Cho-gin, and Keicho Mameita-gin are generically called Keicho Kingin (gold and silver of the Keicho era) and they are positioned as symbolic currencies of the unification of the whole country achieved by Ieyasu TOKUGAWA.
Summary
The surface of Keicho Oban had a writing in ink of 'Ju-ryo Goto' (a kao [written seal mark]), and this seal mark was written by Tokujo GOTO, who was the fifth generation of the Goro family, Tokujo's real younger brother Chojo, Kenjo, who was the seventh generation of the Goto family, and Teijo, the ninth generation of the family. The kao written by Chojo in his early days is reminiscent of a bamboo leaf, and Keicho Oban with his seal mark are called Sasagaki (which literally means "bamboo leaf writing") Oban. Four circled hallmarks of paulownia patterns are carved on the left, right, top and bottom of a Keicho Oban coin and a circled hallmark of paulownia patterns, a pattern of paulownia in a hexagon, and a kao are carved on its back, and the shape of a coin is angular ellipse.
Unlike Tensho Oban, small dots are carved on the surface of Keicho Oban
According to some record, the total amount of Keicho Oban minted is 16,565; however, as 15,080 Meirekiban (Keicho Ogan minted during the Meireki era) were minted, it is not clear what range does this record cover.
Oban was not a currency minted to be used for regular circulation, and it was for rewards and gifts. In case such a coin drifted to the currency market, its value was determined at an exchange shop according to the amount of contained gold and demand for the coin, and as for Keicho Koban and Ichibuban, their value was approximately 7 ryo 2 bu according to their gold content but in the early Keicho era, the market price of Keicho Koban and Ichibuban was 8 ryo 2 bu as a coin used for rewards and gifts. In addition, when a coin's seal mark written in ink faded away, people brought it to an obanza (place to mint Oban) and the writing in Indian ink could be rewritten with the fee of three monme and five bu of silver, or one bu of gold after 1819.
Koban and Bukin were made of mixed metal of pure gold and pure silver, and the amount of contained copper was at impurity level; whereas, about 3% of copper were intentionally added to Oban in order to have the color of gold to make it more aesthetic.
The standard weight was one plate of gold (165 grams), which was equivalent to 44 monme; however, the actual standard weight was 44 monme and 2 bu with additional 2 bu as decrease in the weight at the time of minting and abrasion were taken into consideration. Keicho Oban was in currency was used until 1695, when Genroku Oban started to be used.
Keicho Oban
At first an obanza was established at the northern end of Muromachi-dori Street in Kyoto, and after 1625, obanza were also opened in Edo. Types of oban minted from the Keicho era to the Meireki era are as follows and it is said that each coin is more or less different in its karat.
Ju-ryo Ban
Nijo Ban
Hitotsugoku-in: On the back side one hallmark is carved and the hallmark is one of the following characters: "田" (ta), "ま" (ma), "金" (kin), and "さ" (孫).
Sama Ban: On the back side, two hallmarks of characters 'サ and マ' (sa and ma) are carved.
Nami Ban: On the back side, a hallmark of a combination of two characters selected from the following is carved: 'ゑ・九' (e and nine), 'さ・新' (sa and shin), and '長・新' (cho and shin).
Meireki Oban
The scale of the Great Fire of Meireki occurred in 1657 was so huge that even the castle tower of Edo-jo Castle and Gokinzo (treasure house of Edo-jo Castle) were also damaged. Its shape became less angular, and additionally, dots carved by chisel became coarser and they sloped from right to left. Afterwards, Oban was also minted in the obanza in Kyoto. Every Oban of this variety had the seal mark written in Indian ink by the 9th master Teijo.
Meirekiban (also referred to as Edoban): On the back side, the hallmark of '久・七・新' (kyu, seven, shin) or '九・七・竹' (nine, seven, take) is carved, and this Meirekiban has the bigger number of existing coins than any other Keicho Oban types.
Mitsugokuin: This variety was minted at the obanza in Kyoto in and after the Meireki era. On the back side, a hallmark consisting of three characters is carved and the hallmark is one of the following four combinations: '弥・七・九' (ya, seven, nine), '次・七・九' (nami, seven, nine), '坂・七・九' (saka, seven, nine), and '弥・七・新' (ya, seven, shin).
Yotsugokuin: This variety was minted at the obanza in Kyoto in and after the Meireki era. On the back side, a hallmark consisting of four characters is carved and the hallmark is one of the following three combinations: '次・七・源・九' (nami, seven, gen, nine), '坂・七・源・九' (saka, seven, gen, nine), '弥・七・源・九' (ya, seven, gen, nine).