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Coins in the collection of the Xiji County Coin Museum in the Ningxia Hui autonomous region. [Photo by Ma Wenhai/For chinadaily.com.cn]

Bai Xiaolong, head of the museum, said coins reflect the politics of their day.

"If a country is unified and stable, the coins of the regime or dynasty are unified, such as the dynasties of the Han, Tang, Song and Ming," Bai said.