PHILADELPHIA (AP) — A long-lost version of the Air Force One recordings made in the immediate aftermath of President John F. Kennedy’s assassination, with more than 30 minutes of additional material not in the official version in the government’s archives, has been found and is for sale.

There are incidents and code names described on the newly discovered two-plus hour recording, which predates the shorter and newer recording currently housed in the National Archives outside Washington and the Lyndon B. Johnson Library in Texas. The shorter recording was thought to be the only surviving version of the tape.

The asking price is $500,000 for the reel-to-reel tape, which is inside its original box with a typewritten label showing it was made by the White House Communications Agency for Army Gen. Chester “Ted” Clifton Jr.

It is titled “Radio Traffic involving AF-1 in flight from Dallas, Texas to Andrews AFB on November 22, 1963.”

“As Americans have looked to the history of the Kennedy assassination in search of answers, somewhere in an attic there existed a tape made years before the only known surviving version, of the conversations on Air Force One on that fateful day,” said Nathan Raab, vice president of The Raab Collection, a Philadelphia historic documents dealer that put the tape up for sale.