CHICAGO (March 14, 2013)—Researchers found a rare, 600-year-old Chinese coin on the Kenyan island of Manda, the Field Museum in Chicago announced.

Researchers say the coin proves trade existed between China and eastern Africa decades before European explorers set sail.

The coin, which is made of copper and silver, has a square hole in the center so it could be worn on a belt.

It was issued by Emperor Yongle of China and his name is written on the coin, scientists said.

Scientists from Kenya, Pennsylvania and Ohio also participated in the expedition.

They also found human remains and other artifacts predating the coin.