The Tangut tribe had been vassals to the west of China since the Tang, but in the middle of the Song, their king proclaimed himself emperor of the Western Xia dynasty. Like the Jin and the Liao they often attacked Song. The Western Xia was extinguished by Genghis Khan in 1227.
The legends of their coinage were both written in Tangut and Chinese. The Tangut language is not spoken today, and not all coin legends have been deciphered. 
Both bronze and iron coins were made, and both casting and calligraphy was fine (Peng p. 461-462).