— Two 22-karat gold coins that spent almost five days in Earth orbit have set a new record for the most-ever paid for an artifact or memento flown aboard a space shuttle. The well-traveled currency sold for more than half a million dollars each at an auction on behalf of the U.S. Mint on Friday (Sept. 12).

The pair of Sacagawea dollars were offered alongside five others that were launched on NASA's space shuttle Columbia in 1999. They were carried aboard mission STS-93 to both promote the then-upcoming release of the U.S. Mint's Sacagawea golden dollars and to celebrate the flight of astronaut Eileen Collins, who like the coins' depicted subject, became a trailblazer as a the first woman to command a U.S. space mission.

"That's incredible!" said Collins, reacting to the auction results in an email to collectSPACE. "Space shuttle mission STS-93 still lives on. With the incredible success of the Chandra X-Ray Observatory, which was deployed on this flight and is still sending back unique and astonishing astronomy data, I am happy to see the Sacagawea coins are drawing so much enthusiasm. I am still so proud to have been part of this wonderful mission."

The coins that sold for $550,001 were the sixth and seventh examples to be offered. They were preceded by five others that commanded $380,001; $360,001; $400,001, $420,001 and $500,001, respectively. (For this auction, the buyer's premium was waived such that the hammer price plus $1 for the coin's face value was the sale amount.)

In total, the seven lots brought in $3.16 million. Only five other space shuttle-flown Sacagawea gold dollars exist and they will forever remain in the mint's collection.

"We are honored to auction these rarities," said Chris Ortega, the auctioneer at Stack's Bowers who ran Friday's sale on behalf of the U.S. Mint. "The symbolism of these lots is truly incredible."

"The pattern gold dollars in lots one through seven are the only U.S. coins struck specifically for spaceflight. They celebrate some of the most crucial elements that have enabled our country's success — trailblazing explorers, space age technology and, of course, gold," said Ortega. "If one were to select a single coin to own that embodies America's greatness, this would be it."

Even so, the high bid for each Sacagawea dollar did not come close to ranking among the top 100 sales of U.S. coins, which begin at more than a million dollars and climb to the nearly $19 million spent in 2021 for a 1933 "double eagle" coin.

As space memorabilia, though, all seven surpassed the highest amount paid for an object flown on one of NASA's now-retired winged orbiters. In 2015, an unidentified bidder paid $265,607 for six 24-karat gold plates that were part of the Long Duration Exposure Facility (LDEF). The bus-size satellite was deployed by the space shuttle Challenger in 1984 and returned to Earth on Columbia in 1990.

At least a portion of the gold from that sale was later used in the minting of 2,000 medallions in celebration of the China's Moon Festival in 2015.

Other space artifacts have been sold for upwards of $2.8 million, but those few examples have either been complete spacecraft or were flown to the moon. Most of the items that were carried on the space shuttle orbiters during their 30 years in service and have reached the collector's market have sold for tens of thousands of dollars at most, with the majority typically selling for hundreds of dollars, if not less.

The Sacagawea 22-karat gold dollars were ranked prior to Friday's auction as the fifth most in demand by collectors among the "Top 100 Modern Coins" judged by the Professional Coin Grading Service (PCGS). The same company graded and encapsulated the space-flown coins for the sale.

Each of the winning bidders will receive a certificate of authenticity for their coin signed by the acting director of the mint, Kristie McNally.

Other U.S. coins have been launched into space, including as astronauts' mementos or, in at least one other case, on behalf of the mint. In 2015, Stack's Bowers auctioned a 1793 wreath cent that was flown on NASA's Gemini VII (7) mission for $82,250. In 2018, two curved coins struck to commemorate the 50th anniversary of the Apollo 11 moon landing mission were flown to the International Space Station. One is now held by the U.S. Mint while the other is on display at the National Air and Space Museum in Washington, DC.