Sunken treasure? Divers stumble upon priceless ancient gold.

It is not everyday you go scuba diving and discover a thousand-year-old sunken treasure.

Members of a diving club were exploring the ancient Mediterranean harbor of Caesarea when they spotted a glimmer, what they initially thought to be toy coins. Upon further inspection, they realized they were real and quickly alerted their director, who reported the find a few weeks ago.

Little did they know, their discovery would yield priceless results. The Israel Antiquities Authority unearthed nearly 2,000 mint-condition gold coins, weighing about 20 pounds, that dated as far back as the second half of the ninth century. This is the largest hoard of gold coins discovered in Israel.

“These divers are model citizens. They discovered the gold and have a heart of gold that loves the country and its history,” Kobi Sharvit, the director of the Marine Archaeology Unit of the Israel Antiquities Authority, said in a statement.

Mr. Sharvit believes the gold could have come from many places, and was probably uncovered during shifting seabeds as a result of winter storms.

“There is probably a shipwreck there of an official treasury boat which was on its way to the central government in Egypt with taxes that had been collected. Perhaps the treasure of coins was meant to pay the salaries of the Fatimid military garrison which was stationed in Caesarea and protected the city. Another theory is that the treasure was money belonging to a large merchant ship that traded with the coastal cities and the port on the Mediterranean Sea and sank there,” Sharvit speculated in a statement.

Regardless of how it happened, the Israel Antiquities Authority believes this is a huge archaeological discovery that will hopefully reveal other information about the time period. The gold coins came in a variety of denominations—including a dinar, half dinar, and quarter dinar, of various dimensions and weight—and, according to the Israel Antiquities Authority, is certainly a treasure of the Fatimid Caliphate which ruled much of North Africa and parts of the Levant. The cultural and historical information that can be derived from their discovery—and future discoveries at the site—are priceless.

Many of the coins also display teeth marks, showing the common way merchants tested coins to ensure they were gold and not a less valuable metal. The coins’ preservation was remarkable, due to the fact that gold does not corrode in air or water.

“The coins are in an excellent state of preservation,” Robert Cole, an expert numismatist with the Israel Antiquities Authority, said in a statement. “And despite the fact they were at the bottom of the sea for about a thousand years, they did not require any cleaning or conservation intervention from the metallurgical laboratory.”