The undated postcard of Vero Beach, Florida, addressed "To Steven" and signed by Armstrong, had an estimated value of $700 before the auction. It was one of thousands that the Apollo 11 astronaut signed for fans and collectors for many years after his historic trip to the moon in July 1969.

Armstrong died on August 25 at the age of 82 after complications from heart surgery.

"Like the Apollo 11 rocket ship, Neil Armstrong autograph prices seem to be blasting through the stratosphere. Signatures have tripled in value and signed photos have doubled in just a matter of days. The demand for his autograph yesterday was unprecedented," said Nate Sanders, owner of Nate D. Sanders Auctions.

Sanders said Armstrong signed photos until the mid 1980s with each autograph selling for around $8 to $12 each.

Sanders said three different Apollo 11 glossy photos signed by the whole crew, which included Armstrong, Buzz Aldrin and Michael Collins, sold for $7,361 each at Thursday's auction.

(Reporting By Jill Serjeant)

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