Tang Dyn. Kai Yuan Tong Boa H14.4a

Tang Dynasty Cash - anonymous Middle type with a high left shoulder in 'yuan' (718 - 732 A.D.). Reverse is the flat line above the hole. Its 25 mm and 4.27 g. David Hartill H14.4a
Kai Yuan tong bao (The Inaugural Currency), these were the main coin cast for the dynasty, a period of nearly 300 years and a high point in Chinese history and culture. The legend was written by the famous calligrapher Ouyang Xun in a mixture of styles known as 'bafen' and 'Li' and looks like official or clerkly style writing. It is the first coin to use the term 'tong bao.' The execution of this coins was so admired that it served a a model to be emulated over many regimes and over later periods. Kai Yuan tong bao characters are read: top, bottom, right, left.
These coins are said to be struck from the begining of Huichang's era in 841 (used from the melted materials of destroyed Buddhist monasteries), to late 841, when the 'Chang' was to be replaced by a mintmark.
The only confirmed mint is Yangzhou (they were the original ones to get permission to cast these), but seeing how common these are, there are two possibilities: 1) 'Chang' was used posthumously as a mintmark for Yangzhou, which does not have its own type with a mintmark, or 2) the 'Chang' was adopted by other mints. The latter seems quite likely, where as the former is still possible (while the other mints changed mintmarks, Yangzhou could have retained the 'Chang').