— How much can a rarely sought after astronaut's autograph add to the value of a relatively common, yet flown-in-space item? If one example is any guide, it is thousands of dollars.

The item, a stamped and cancelled envelope that flew on the eighth flight of the space shuttle, is —absent any signatures — not at all rare. In 1983, NASA packed more than 260,000 similar envelopes on the space shuttle Challenger to mark the agency's 25th anniversary.

After the mission, the United States Postal Service (USPS) offered each "cover" (as they are referred to by collectors) for $15.35 by mail order. On any given day on eBay today, more than 40 years later, you can find the STS-8 covers selling for sometimes slightly more, but just as often less than their original retail price.

So why did the astronauts' autographs on the $6,500 cover sold by RR Auction on Thursday (Oct. 22) result in the much higher result? Well, that comes down to its former owner and his signature.

'We, the crew of STS-8'

Of the more than a quarter of a million covers that were carried on Challenger's STS-8 mission, only 10 did not fly in the winged orbiter's payload bay. Rather than be stowed in storage boxes and canisters in the exposed-to-a-vacuum cargo hold like the rest, this special set was flown inside the crew cabin and were intended for post-flight presentation to the President of the United States Ronald Reagan, Vice President George Bush, Postmaster General William Bolger, NASA's administrator Jim Beggs and the five STS-8 crew members.

Commander Richard "Dick" Truly, pilot Dan Brandenstein and mission specialists Guy Bluford, Dale Gardner and William "Bill" Thornton further distinguished the 10 covers by autographing them and agreeing not to sign any others.

"Due to the number (over 1/4 million) of the flown covers and resultant increase in value of signed covers, we the crew of STS-8 are not signing any flown covers. Our work load does not allow for signing that many covers," Brandenstein wrote, explaining the situation in a hand-written letter sent to a collector after the flight.

As the years passed, Brandenstein and three of his crewmates either forgot or let the voluntary restriction fall by the wayside. After they retired from NASA, they could do as they pleased and if there was ever going to be a crushing demand for their autographs, it was immediately after the covers went for sale. In the decades since, they could handle the periodic collector's request.

That is, except Thornton. He held to the agreement, explaining to collectSPACE in 2003 that the only way he would feel comfortable signing any STS-8 flown cover would be if NASA issued him a letter formally permitting him to do so. A NASA spokesperson replied by saying that the agency was not in the practice of issuing instructions to its former employees.

Thornton died in 2021 at the age of 91, and is believed to have never autographed any other STS-8 flown cover than the original 10. The complete crew-signed example that was sold on Thursday was his cover out of that set, offered along with other items from his estate.

Second sale, first sold

Of the crew-signed STS-8 flown covers, Thornton's is serial number 9. It was the first of the cabin-flown 10 to be sold by its original recipient, but the second to sell.

In 2021, two months after Thornton died, cover number 3 popped up on eBay. For at least one collector, the sale raised concerns that the offered cover might have been stolen and after some inquiries, discovered that Truly, STS-8's commander, had never received his cover after the flight. The collector bid on and won the cover for $1,801.76 and then mailed it to the former astronaut, who was happy to finally have one.

Thornton's cover, therefore, is really the first cover to properly change hands. The $6,529 is also believed to be the most ever paid for a space shuttle flown cover from any mission.

RR Auction's sale included 60 lots from the Thornton estate. While the signed and flown cover brought in a respectable amount, it was outperformed by several of the late astronauts' gold and silver flown medallions, including examples that were carried on Apollo 11, Apollo 13 and STS-1.

The top selling item among the Thornton consignments, though, was his 1967 Plymouth Belvedere GTX muscle car, which commanded $36,500 (including the buyer's premium). Thornton used it to challenge fellow astronauts in impromptu road races, including the first American in space, Alan Shepard.

The auction in total offered 371 lots, spanning the entire history of spaceflight and exploration. That included an Apollo 11 crew-signed flown-to-the-moon cover that sold for $27,225 and the wrist checklist that Gene Cernan used during his second of three excursions on the moon during the 1972 Apollo 17 mission, which alone brought in $408,000.