What are the words with two lines on the ancient coin?

Coin year. According to the personal library network, reading coins from top to bottom and from right to left is called direct reading or sequential reading. Fate Bao Tong, Kaiyuan Bao Tong, etc. All the years are the year numbers of coins. The early form of ancient coins was mainly shell coins. In China, in the late primitive society, the main currency form in Zhixia, Shang and Zhou Dynasties was physical currency, and natural shellfish were widely circulated. Later, a small amount of metal weighing money and coins appeared.