ANCIENT CHINA The Tang Dynasty 618-907 AD Kai Yuan Tong Bao, Nail mark Crescent
The Tang Dynasty 618-907 AD Kai Yuan Tong Bao
A crescent-shaped mark is often found on the reverse of Kai Yuans. The legend is that the Empress inadvertently stuck one of her fingernails in a wax model of the coin when it was first presented to her, and the resulting mark was reverentially retained. Other imperial ladies have also been proposed as the source of these nail marks, especially the Imperial Consort Yang. Peng explores the possibility of a foreign source for them. More prosaically, they appear to be a control system operated by the mint workers.
Reference: Hartill 14.4
Kai Yuan Tong Bao (Chinese: 開元通寶; pinyin: kāiyuán tōng bǎo; literally: "The Inaugural Currency") were the main coin issued by the Tang. It was cast for most of the dynasty, a period of nearly 300 years. It was first issued by the Emperor Gao Zu in the autumn of the 4th year of the Wu De period (August 621). Its diameter was to be 8fen. The weight was set at 2.4 zhu, ten to the liang. 1,000 coins weighed 6 jin 4 liang. The legend was written by the famous calligrapher Ouyang Xun in a much admired mixture of the Bafen and Li (official or clerkly) styles of writing. This is the first to include the phrase tong bao, used on many subsequent coins. The inscription was used by other regimes in later periods; such coins can be distinguished from Tang coins by their workmanship. Minting and copper extraction were centrally controlled, and private casting was punishable by death. For the first time we find regulations giving the prescribed coinage alloy: 83% copper, 15% lead, and 2% tin. Previously the percentages used seem to have been on an ad hoc basis. Actual analyses show rather less copper than this.