A signed agreement known as space exploration's "Magna Carta" comes to auction at Heritage on June 3 following two days of internet bidding.
The Apollo-Soyuz document, signed in July 1975, was the start of cooperation between the Soviet and US space programmes.
Written in English and Russian, the document is one of four copies and paved the way for future collaboration, recently exhibited in the fond farewells seen at the International Space Station.
It was the first document signed in space, and followed the historic docking of the Apollo and Soyuz spacecraft, the first time two spacecraft had met.
Signed by the entire crews of both missions, it has a high end estimate of $50,000.
The document reads:
"This is to certify that at 12 hours 09 minutes Washington time and 19 hours 09 minutes Moscow time, on July 17 1975, flight crews of the United States of America and the Soviet Socialist Republic successfully docked their Apollo and Soyuz spacecraft in Earth orbit.
"They share the hope that this first international manned space flight will stand in the light of history as a significant advance in the ability of their nations to work together in ways that advance the interests of people everywhere."
A painting of Apollo 16's John Young on the moon by Alan Bean will also feature prominently at the sale. It has a high end estimate of $200,000 and is sure to interest alternative investors due to the artist's popularity.
The Distinguished Flying Cross and flown mustard seeds of astronaut Ed White, the first American to walk in space, will also star at the auction.
The items are expected to sell for $16,000-20,000.
- Click here to view our space and aviation stock items for sale
- Learn how you can get pleasure and profit by investing in space memorabilia
- Read all the latest Space and Aviation news
Join our readers in more than 200 countries around the world - sign up for your free weekly Collectibles Newsletter today