have been printed sometime during the reign of Emperor Renzong of Western Xia (1139–1193). It is considered by many Chinese experts to be the earliest extant example of a book printed using wooden movable type. Metal movable type China At least 13 material finds in China indicate the invention of bronze movable type printing in China no later than the 12th century, with the country producing large-scale bronze-plate-printed paper money and formal official documents issued by the Jin (1115–1234) and Southern Song (1127–1279) dynasties with embedded bronze metal types for anti-counterfeit markers. Such paper-money printing might date back to the 11th-century jiaozi of Northern Song (960–1127). The typical example of this kind of bronze movable type embedded copper-block printing is a printed "check" of the Jin dynasty with two square holes for embedding two bronze movable-type characters, each selected from 1,000 different characters, such that each printed paper note has a different combination of markers. A copper-block printed note dated between 1215 and 1216 in the collection of Luo Zhenyu's Pictorial Paper Money of the Four Dynasties, 1914, shows two special characters – one called Ziliao, the other called Zihao – for the purpose of preventing counterfeiting; over the Ziliao there is a small character (輶) printed with movable copper type, while over the Zihao there is an empty square hole – apparently the associated copper metal type was lost. Another sample of Song dynasty money of the same period in the collection of the Shanghai Museum has two empty square holes above Ziliao as well as Zihou, due to the loss of the two copper movable types. Song dynasty bronze block embedded with bronze metal movable type printed paper money was issued on a large scale and remained in circulation for a long time. The 1298 book Zao Huozi Yinshufa () by the Yuan dynasty (1271–1368) official Wang Zhen mentions tin movable type, used probably since the Southern Song dynasty (1127–1279), but this was largely experimental. It was unsatisfactory due to its incompatibility with the inking process. But by the late 15th century these concerns were resolved and bronze type was widely used in Chinese printing. During the Mongol Empire (1206–1405), printing using movable type spread from China to Central Asia. The Uyghurs of Central Asia used movable type, their script type adopted from the Mongol language, some with Chinese words printed between the pages – strong evidence that