Omega has donned the wrists of more than a few action heros, including James Bond, but the real life supermen that donned the timepieces as tool watches in NASA’s space program are perhaps the most exciting “brand ambassadors,” if you can call them that. Now one of the ultra-rare Omegas owned by one of the astronauts is coming up for sale in what could be a once-in-a-lifetime event.

Wind Vintage is putting astronaut Scott Carpenter’s 18-karat gold Speedmaster 145.022-69 BA up for sale. Carpenter was not only an astronaut, he was an aquanaut, aeronautical engineer, test pilot, naval officer and aviator and was one of seven astronauts selected for NASA’s Project Mercury, the first human spaceflight program in the United States, in April 1959. A decade later, America would put the first man on the moon and to celebrate that epic historical moment an Astronaut Appreciation Dinner was held by NASA in Houston to celebrate not only the landing, but also the entire American space program. To honor the guests, Omega created its first 18-karat gold Speedmaster Ref. 145.022 BA to gift to astronauts at the event (President Nixon and Vice President Spiro Agnew were also gifted the timepieces, but were legally unable to keep them and they ultimately reside in the Omega museum in Bienne, Switzerland).

Carpenter’s watch is number six of the 30 pieces that were made and comes with his name specially engraved on the caseback, his space mission and a special message that reads “to make man’s conquest of space with time, through time, on time.” The astronaut passed away in 2013 and the watch has come to market directly from one of Carpenter’s family members. According to Eric Wind, owner of Wind Vintage, this is the “holy grail” of Omegas and there is evidence to back that up. Just last year, astronaut Will Schirra’s commemorative gold Speedmaster sold at auction for US$1,907,954 (HK$14,976,580) and that one came from the second owner who had purchased the piece from Schirra’s family.

The listing price for Carpenter’s prized gold Speedmaster comes in at US$1.5 million (HK$11,774,347), which seems like a bit of a bargain—comparatively speaking, of course. Unlike Schirra’s Speedy, this one is not up for auction, which means that it will be first come, first serve and, as a historically important piece, likely won’t be around for long.