Neil Armstrong’s EKG taken the moment he first set foot on the Moon is available to the highest bidder by the New Hampshire-based auction house RR Auction starting May 16.

Though only listed at $3,000, the electrocardiogram, last went for $12,500 in an April 2004 auction.

Perhaps one of the most noteworthy aspects of the EKG is just how steady it remained while Armstrong made the world-changing step.

“It was really slow on the way down, while Aldrin’s was racing,” Gerald Schaber, the one tasked with monitoring Armstrong’s heartbeat at the time, told The Guardian. “But that was typical of Neil. Just like the first thing he really said was, ‘Houston, we have engine shut down here,’ really calmly. Mission control told him to speak again. It was then he said, ‘The eagle has landed’ for the TV networks. He was just that cool.”

That cool head came in handy in his 1966 journey as commander of the Gemini 8 mission, which nearly ended in disaster when a thruster rocket malfunctioned, causing the spacecraft to spin wildly out of control. As it approached and possibly exceeded a rate of one revolution per second, Armstrong, along with crew member David Scott, successfully managed to engage all 16 reentry control system thrusters in order stop the spinning.

Armstrong passed away last year at the age of 82 due to complications related to heart surgery.

Other items up for sale include Buzz Aldrin’s “constant wear garment,” as well as the Apollo 11 command module rotation hand controller grip and the Apollo 11 commemorative sword.

About the EKG, Jay Walker, curator and chairman of TEDMED, said in a 2012 presentation, “In a thousand years this will be an amazing artifact, because we saw, at the moment man landed on the moon – we were monitoring their vital signs back on the Earth, which is something we will all be doing, as a matter of course, in just a few years for all of us and our loved ones.”