The bizarre facts will once more stir dark suspicions about an event that remains one of the enduring episodes of the 20th century, the murder of a young president in his prime apparently by a lone killer with an ageing rifle. Had he lived, President Kennedy would now be 82.
The coffin carried the president's body back from Dallas to Washington after he was assassinated in 1963 in circumstances that have triggered a thousand conspiracy theories. It was damaged en route, and another mahogany casket substituted for the burial of the president.
The details of its final fate are part of a huge tranche of documents to be released by the National Archives in Washington, including vast amounts of declassified CIA papers on Lee Harvey Oswald, the man accused of the killing, Cuba and other matters.
The coffin was kept for a year in storage, and then picked up by a Government truck and never seen again.
It was kept for another year, and then flown in a military plane out over the ocean off the coast of Maryland and Delaware.
It was dumped in an area previously used for disposing of ammunition and weapons. The supposed rationale for the disposal was that the authorities did not want the coffin to become a relic sold on the open market.
Few of those who have tracked the investigations into the president's death were satisfied with this explanation. "The coffin is evidence just like the body is evidence," David Lifton, author of a book on the Kennedy killing, told the Associated Press. "You don't destroy evidence." Other witnesses say that the president's body was in fact transported in a third coffin, a utilitarian metal casket.
A Texas politician, Earle Cabell, suggested the disposal according to the records. "It is an extremely handsome, expensive, all-bronze, silk- lined casket, and fortunately, and properly, was paid for by the General Services Administration, and presently is in the possession of GSA," he wrote. "This item has ... value for the morbidly curious. And I believe that I am correct in stating that this morbid curiosity is that which we all seek to stop."
There has been frequent speculation - including in the film JFK by director Oliver Stone - that Oswald was not the assassin, or at least not the only one; that US government agencies colluded in either the killing or a cover-up; and that the subsequent investigation by the Warren Commission either ignored or was not provided with crucial evidence. It is partly in an effort to clear up such suspicions that the evidence is now being released.
But the news merely sparked a fresh round of speculation amongst those obsessed by the Kennedy affair. Internet chat rooms filled with dark theories, amongst them that the president was never buried at Arlington National Cemetery at all; that the disposal of the coffin was related to alleged mysterious changes in the medical condition of the president's body; and that Mr Cabell was related to those who might have plotted against the president.
His brother, General Charles Cabell, had been the Deputy Director of the CIA, and a pivotal figure in the abortive Bay of Pigs invasion of Cuba.