Vietnamese Coin
Minh Dao Thong Bao

December 12, 1998
This coin is listed in the Timeline and imperial coinage of Vietnam, because Do Van Ninh in his book Annam ancient coin wrote about. According to him, Minh Dao thong bao were mentioned by peoples but he never sees any, but Minh Dao nguyen bao. His rational is that historians said about Minh Dao without mentioning about nguyen bao or thong bao. Chinese did not cast Ming Dao Tong Pao, so if thong bao will be found, it should be a Vietnamese coin.
Two images from Fisher's Ding (unconfirmed coins section, N2747 & N2748):

Chinese Coinage Web Site