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An Ōban 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.
- Metzler p.15
- The Cambridge History of Japan: Early modern Japan by John Whitney Hall p.61 
- Mark Metzler (2006). Lever of empire: the international gold standard and the crisis of liberalism in prewar Japan. Volume 17 of Twentieth Century Japan: The Emergence of a World Power. University of California Press. ISBN 0-520-24420-6.