An Ōban (大判) was a monetary ovoid gold plate, and the largest denomination of Tokugawa coinage. Tokugawa coinage worked according to a triple monetary standard, using gold, silver and bronze coins, each with their own denominations.
The first Oban – Tenshō Ōban (天正大判) – were minted by the Gotō family under the orders of Hideyoshi in 1588.
The Tenshō Ōban was equivalent to ten Ryōs, or ten Koban (小判) plates, with a weight of 165 g.
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Text from the Wikipedia article “Ōban”, available under CC BY-SA 4.0.