The Field Museum in Chicago announced the find Wednesday. The joint expedition was led by Chapurukha Kusimba of the museum and Sloan Williams of the University of Illinois-Chicago. Researchers say the coinproves trade existed between China and eastern Africa decades before European explorers set sail.
The coin is made of copper and silver. It has a square hole in the center so it could be worn on a belt. Scientists say it was issued by Emperor Yongle of China and his name is written on the coin.