Four chinese characters Da Ding Tong Bao / Four protrusions from the corners. 25mm, 4.24 grams. Schjöth #-; Hartill 18.56 (for iron cash).
A unique item - a copper coin cast in the dies for an iron coin (for this type of an iron coin see Hartill 18.56). This is either a copper mother cash for an iron cash or (more likely, in my opinion) a trial casting. It is different from the normal Da Ding's - the inscription is VERY different in execution and a different reverse. This piece is probably form the mint of Zhili in Xinjiang.
The Jin Dynasty, also known as the Jurchen Dynasty, was founded by the Wanyan clan of the Tartar Jurchens, the ancestors of the Manchus who established the Qing Dynasty some 500 years later. The Jurcheds carved a large Kingdom out of the Song realm and controlled the northern half of China for over a century, with the southern part controlled by the Song dynasty. The Kingdom came to an end when an allied army of Song and Mongols looted the capital in 1233, and the next year Jin Emperor Aizong committed suicide to avoid being captured. The territory of the Jin was to be divided between the Mongols and the Song.
This coin is unconditionally guaranteed to be authentic.