China: cast bronze cash coin, Tang Dynasty, Anonymous Middle Type, ca. 718-732 AD Obverse: KAI YUAN TONG BAO. Reverse: Crescent above central square hole. 24 mm, 3.37 g. Ex- Kenneth W. Dorney Ancient Coins & Antiquities, June 2019. He attributed this as "Hartill14.6u".
TANG DYNASTY China Tang 718-732 CE AE Cash Kai Yuan Tong Bao - Crescent H 14.3 China Tang 845-846 CE AE Cash Kai Yuan Tong Bao - Luo H 14.77 China Tang AE Cash H 14.101
I'm checking in my copy of Hartill's Cast Chinese Coins and I believe the reference number is off, the Middle Type is 14.3, 14.4, and 14.5 with 14.4 being the left shoulder yuan variety which matches your coin. Yours also has a neat line on the reverse called a nail mark. I couldn't find an exact match like yours on Zeno but it would be somewhere under this category. The combination of the crescent above and nail mark below would probably make it worth a little bit more I would suppose.