Back in the 1970s, several Apollo astronauts were the subject of disciplinary action by NASA - with a collection of postage stamp covers providing a key item of evidence.
Among them was Apollo 15's Commander David Scott and Lunar Module Pilot James Irwin, respectively the eighth and ninth men to set foot on the Moon.
That two such men, among NASA's bravest and finest, could be involved in such a disciplinary is remarkable. But so is the story behind how it happened...
When Apollo 15 - man's ninth manned space mission, and the fourth mission to the Moon - blasted-off on July 26, 1971, there was a secret stashed aboard the command module.
The crew brought 398 commemorative postage stamp covers with them on their trip to the Moon, with the intention of selling some of them to a German stamp dealer, named Hermann Sieger, after returning to Earth.
Out of the stamp collection, 100 would be sold to the German dealer, with the other 298 kept by the crew themselves as souvenirs.
Scott, Irwin and Command Module Pilot Alfred Worden's mission was, of course, a success. Scott and Irwin spent three days on the Moon, and a total of 18½ hours outside the spacecraft.
What's more, the crew were able to travel much further from their landing site than before thanks to the new Lunar Rover. With the four-wheeled buggy, the pair were able to collect a total of 77kg of lunar surface material.
Despite some minor parachute failure, Apollo 15 landed safely back on Earth to a hero's welcome. Meanwhile, behind closed doors, the deal with the Hermann Sieger was finalised...
Everything had apparently gone to plan. That is, until word of the illicit stamp deal leaked into the public domain soon after the mission.
The crew's stamps were duly confiscated by NASA, and became known as the "Sieger covers" once the details of their arrangement with the German stamp dealer were revealed.
Congress took notice, and disciplinary action followed. David Scott admitted to carrying the stamps during the subsequent proceedings.
Meanwhile, former Apollo 13 crewman Jack Swigert was dropped from the Apollo-Soyuz Test Project. Although he wasn't involved with the controversial Apollo 15 stamp deal directly, evidence related to similar schemes built up against him.
It eventually emerged that the astronaut's profits would have been used to set-up trust funds for their children - an arrangement which was in no way illegal, and which NASA had actually turned a blind eye to in previous space flights.
Neither was it illegal, nor prohibited by NASA at the time, to take souvenirs up into space. Apollo 15 actually had 243 covers on-board which were authorised by NASA, along with the 398 unauthorised covers.
But Scott, Worden and Irwin were deemed an embarrassment to NASA and the Apollo program, and subsequently made an example of. The trio were dropped as the planned back-up crew to Apollo 17, and this effectively ended their career as astronauts.
Nevertheless, a decade later in 1983, debate surrounding the 243 "authorised" covers would see events take a different turn. That year, the crew of Apollo 15 successfully filed a lawsuit against the government for the return of their 298 unauthorised covers.
Citing NASA's partnership with the US Postal Service to sell covers flown in the space shuttle - essentially a 'big business' arrangement identical to the crew's own planned deal - Scott, Worden and Irwin won the case and had the covers returned to them.
Today, the scandal surrounding the Sieger covers has only added to the stamps' values among both space memorabilia and stamp collectors. In 2008, one of them sold at a Novaspace auction for $15,000.
Meanwhile, Commander David Scott has since been awarded two NASA Distinguished Service Medals, the NASA Exceptional Service Medal, two Air Force Distinguished Service Medals, and the Distinguished Flying Cross.
Like fellow Moonwalkers Neil Armstrong, Buzz Aldrin and the other nine men who set foot on the Moon, David Scott's signature remains a great a sought-after investment - and an especially rare example, signed on a Nuclear Test Treaty no less, is currently for sale to collectors.
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