An operation to transport an estimated half-a-billion dollars in silver and gold coins is expected to take place as early as Friday night, when US military and government officials will secure some 100 miles of southern Florida highway to ensure the Odyssey treasure makes it safely on board two Spanish cargo jets waiting at a Tampa air force base.

Spanish archeological experts were expected late Thursday to complete their inventory of the estimated 594,000 ancient coins and other artifacts that shipwreck hunter Odyssey Marine Exploration plucked in 2007 from the remains of the Nuestra Señora de las Mercedes, sunk in 1804 by the British navy off the coast of Portugal.

At press time, more than 70 percent of the 17-ton cargo, which is being stored at a secret warehouse in Sarasota, had been inspected by scientists from the National Museum of Archaeology and National Museum of Underwater Archaeology, who arrived earlier this week.

Last-minute attempts to keep Spain from repatriating the treasure were still being made before the US Supreme Court. This time, the government of Peru filed a “recall” request of the trove before the justices in Washington late Tuesday. Peru has long argued that because the coins were minted in the former Spanish colony, it is the rightful owner of the currency. The Supreme Court has already denied two emergency petitions by Odyssey and a descendant of one of the military officers on board La Mercedes to prevent Spain from getting the coins.

A federal court in Tampa, which in 2009 originally awarded Spain possession of the treasure, has ordered the US Marshals Service to accompany the coins and other artifacts from the Sarasota warehouse to MacDill Air Force Base in Tampa, where two Hercules C-130 transport planes arrived Thursday to take the treasure home. The entire operation is shrouded in secrecy, but government officials have said they want to get the treasure out of the country as fast as they can.

“The US Air Force has an excellent relationship with the Spanish Air Force and is working closely with them to ensure a safe and secure mission,” said a brief statement issued by MacDill. The court gave Spain a three-day period, which ended Thursday, to inspect the treasure to ensure everything was in order before it could take the coins home.