Mu Qing Tong Bao
1 cash coin

Coin image provided by Goh Khun Liang (New Zealand)
Mu Qing Tong Bao Copper Treasure of the Stately Purity
Zhi Zheng Reach of Straightness

Diameter: 19 mm
Weight: ... g

It is the sacrificial coin of the Yuan Dynasty.
In the Cash coin index, compiled by W.Op den Velde, we can found next information, based on the article of Sun Chung Hui "A study of the temple coins of the Yuan Dynasty", China Numismatics, 1986-1, p.43-48:
    Most of the time coins were made as sacrificial offerings to use in the temples. These sacrificial coins were as official as those from official mints. In the Yuan Dynasty to mint coins was not profitable. So there were no private minting activities. The temple's wealth enabled them to cast coins regardless the high costs. Besides, it served them as a pretext to ask for more funds from the Royal court. The temples had their own foundries, first to make huge bells and copper statues. Sacrificial coins were also produced there, but the workmanship of mintage was inferior to that of professionals. So there are mostly crude, poorly made, and the characters are often in hasty, careless writing. So far no record has been found about the production, usage and circulation of sacrificial coins. In the past there have been notions of so-called Internal-organ coins to be stringed and coiled inside the Buddhist statues to represent the internal organs. So far no evidence to verify this assertion has been found. Most of the Buddhist statues were hollow, made of silk linen painted with layers of lacquer.
    In 1965 a great quantity of Ming Dynasty paper money was discovered inside the Buddhas in the White Dagoba temple in Peking. Since the Tang Dynasty it has been a custom to offer coins before Buddha statues and altars. Sacrificial coins were stringed and hng besides the niche, as to pray for freedom of illness. The offerings were taken away and divided among the monks. The sacrificial coins might be divided into the following categories:
    1. coins bearing a reign title.
    2. coins bearing a reign title and the title of the empire.
    3. coins bearing the title of a famouse Buddhist priest.
    4. coins bearing the name of a temple.
    5. coins with the name of a Buddhist scripture.
    6. coins to be used by pilgrims.
Mu Qing is a hall in the White Dagoba temple, Peking.

Any additional information highly appreciated.
Chinese Coinage Web Site