Ancient coins, a map with an "X," a secret cave: It sounds like something out of a kid's book. Instead, it's an Australian professor's archaeological quest. During World War II, a soldier stationed on the Wessel Islands off northern Australia found several mysterious coins in the sand. Years later, a museum pegged their age at about 1,000 years old, the Age reports. That's when the former soldier marked the location of his discovery on a map with an "X."
Now, Aussie anthropologist Ian McIntosh wants to know more. The coins are from between 900 and 1300 AD and apparently come from an African island off Tanzania; they're among the first ever made in sub-Saharan Africa, McIntosh says, and they suggest foreign explorers could have arrived in Australia far earlier than previously believed. During a Wessel Islands trip in July, McIntosh will investigate the X-ed location—and he'll search for a nearby cave mentioned in Aboriginal legends, supposedly filled with coins and weapons.