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Japanese kozuka, with a nanako ground, inlaid with three mythical beasts, in gilt, length:
Raw copper with natural impurities, including yamagane, and highly refined copper (akagane, motogane) have been known from early times, and the alloys can be traced back between 300 and 900 years, or possibly as much as 1200. Shakudo, for example, may be referenced back to at least the 12th century. Shibuichi has a history of 550–750 years, with samples known from the 1630s.:94 Due to the precious metal content, shakudo and shibuichi were always used sparingly, for small fittings on weapons, doors, small containers, or furniture.
The single most common historical usage was on the fitting known as a tsuba that is fitted below the pommel of the swords carried by samurai and the shōgun, and in fact the banning of ceremonial sword-wearing under the Meiji Restoration had a material impact on production of the irogane metals.