Southern Song

The coins I've seen from that dynasty are usually blank on the reverse.

I know nothing of Chinese coins and the ony southern song I know is Dixie.

This is Hartill 17.47 or 17.48 (S.688) rated common. The difference between the two numbers is based on the degree to which the bottom character Yuan's legs come together at the crossbar. Such differences make a difference to Chinese collectors but not to me. My guess is 17.48 but I do that with 50% certainty. I've tried to get interested in Chinese cash but it is not a major interest to be sure.

Thank you for your comments! The 'crescent moon' and the 'star' (appearing as a dot) were quite common for coins of this dynasty. Explanations of their possible meaning are shown below and are taken from the excellent website Primaltrek.com:-

"Traditional Explanation for the Moon Symbol
There have been a number of theories as to the meaning of these symbols and as to why they appeared on Chinese coins For example, the most popular explanation for the appearance of "moons" was that they were made by a person (usually said to be an Empress or some other famous personage) impressing their fingernail into the clay coin mold before it had dried. This would be similar to what famous actors and actresses of today do when they impress their hands in wet concrete in front of what was formerly the Grauman's (Grumman's) Chinese Theatre in Hollywood.

Another Meaning of the Chinese Character for "Star"
According to old Chinese texts, the Chinese character for "star" (xing 星) not only referred to the lights in the night sky but also had the meaning of 布 (bu) which meant to spread or disseminate. Other ancient texts gave the meaning of star as 散 (san) which had the similar meaning to distribute or to give out.

Coins, as a form of money, represent power and the ancient Chinese believed the key function of a coin was to be distributed or circulated. The implied meaning of the star symbol, therefore, is that Chinese coins should be like the star-studded sky, widespread, numerous and distributed throughout the world."

Later in the Song Dynasty (about 1180) a number indicating the year of the period title in which the coin was cast ( the Emperors reign) was added to the reverse side of the coins. This was done to deter the illegal casting of private coins!