BOSTON -- Bids are already astronomical for a Neil Armstrong check written just before the historic Apollo 11 space flight and they may even go higher.

Apollo 11 40th Anniversary Interactive | Video

Bids are already up to $17,122 for the check Armstrong wrote for $10.50 to Harold Collins, NASA Chief of Mission Support, to repay money he had borrowed.

Sellers said the astronaut handed the check to Collins on launch day in July 1969 as he prepared to leave on the mission that would make him the first man to walk on the moon.

"Here's a check for the loan, but don't cash it, because I WILL be coming back," Armstrong said to Collins.

It is one of the only known Apollo-era checks belonging to Armstrong and its signature includes his middle initial and is one of only a handful of items signed in full by Armstrong.

It is being displayed through July 15 at www.rrauction.com in commemoration of the 40th anniversary of Armstrong's historic moon walk.

"This is probably the coolest Apollo 11 autograph in private hands," said Bobby Livingston of RR Auction, based in Amherst, N.H. "Here's Neil Armstrong rocketing to fame, and he wanted to make sure he paid his debts in case anything happened. He wrote it at the crew's headquarters on July 16, 1969, just hours before he commanded the first manned lunar landing mission in history."

Livingston said that RR Auction obtained the signed memorabilia through Noah Bradley, who bought it at auction from Harold Collins' son George in 2004.

George Collins told Bradley that on the morning of the launch, Armstrong made out the check and told Collins that it should be cashed only if he died in space.