The formation of green rust is different in the north and south, and the oxidation degree in acidic areas of geological belt is also serious. When the north is dry and there is little rain, the rust color is hard when it is not easy to dry. It is rainy and humid in the south, and the oxide layer is loose, mostly blue-green. For example, coins in the Southern Song Dynasty were issued in the south, and more were unearthed in the south. Due to the influence of geographical environment, coins are generally blue-green.
The characters on metal coins such as knives, cloth and money in the pre-Qin period were all written in big seal script. During the Qin and Han Dynasties, Qian Wen's calligraphy style belonged to the category of Xiao Zhuan, such as Banliang, Wuzhu, etc., but it had Han Li style, among which Mangqian was the hanging needle seal. The calligraphy style of Wei, Jin, Southern and Northern Dynasties is complicated. Coins in the Tang Dynasty were written in eight official languages, which prevailed after the Tang Dynasty. In the Five Dynasties and Ten Kingdoms, authenticity, seal and official script were the main characters.
Coins in the Northern Song Dynasty include seal script, official script, truth, line and grass. From Shao Xi, Song Guangzong to Yuan, Ming and Qing Dynasties, Qian Wen mainly used regular script (original script), and occasionally used seal script and official script. Because China is a multi-ethnic country, there are also minority languages such as Mongolian, Manchu, Hui and Tangut in Qian Wen.
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