Unknown Chinese Coin #3

Tang dynasty, Kai Yuan Tong Bao, made for pretty much the full duration, c. 618-907 AD. The crescents are poorly understood; Chinese legend states that this became a good luck ritual after the Emperor's wife accidentally pressed her nail into the wax mold used to make the mother coin. They may or may not have been made by human finger nails, and were probably control marks that made sense to the mint workers.

E: The coins both look authentic. These are only a little less common than the Wu Zhu coinage, and are dirt cheap.

Finn is correct with the coin ID. This is a Kai Yuan Tong Bao. Those cresents aren't from the cool story though. :) These coins (with Dong Guo on the reverse) were really what brought solid coinage here to Korea. Either way, there are varients with that cresent on the top, bottom, left, and right (at least here in Korea). They are more or less just a different series/varient mark that the Chinese did on purpose. Those cresents are used all over the differnt cash coins here in Korea as well. I am pretty good at Chinese characters, so I will look at your other posts and see if I can help.