Was the dust a bust?

A near 200-year-old seemingly empty time capsule unearthed at the US Military Academy might yield a fascinating untold truth about the Army’s fabled ground — rather than simply draw comparisons to reporter Geraldo Rivera opening Al Capone’s vacant vault on live TV in 1986. 

West Point Superintendent Lieutenant General Steven Gilland even joked about the empty Capone vault moments before the bare box was pried open Monday before a packed campus auditorium.

The “superman” grade-lead container — strong enough to block detailed X-ray exams beforehand — possessed nothing but silt, broken indistinguishable materials and an exterior maker’s initial, but experts at academy say the battle’s not over yet.

West Point’s first known time capsule, discovered during recent renovations to the base of a campus monument honoring Thaddeus Kościuszko, may actually reveal a centuries-old secret about the Polish military engineer and American Revolution figure.

“It’s a possibility that it’s his ashes,” USMA Command Historian Jennifer Voigtschild told The Post of Kościuszko.

The ashes theory — one of many hypotheses racing through the minds of bewildered military history experts — could be supported by the USMA library archive, which has 19th century images that refer to Kościuszko’s monument as a “tomb.”

“We’ve always been like, ‘Oh, that’s an error,” Voigtschild said following the sudden “woah!” moment inside Thayer Hall’s packed Robinson Auditorium.

The hall was named for Sylvanus Thayer — the “father of the Military Academy,” who was West Point’s superintendent when Kościuszko’s monument was conceived and erected in the late 1820s.

Thayer died in 1872.

“Thayer was not buried here either — and he was reinterred here,” Voigtschild noted.

Adding to further speculation, the West Point Museum had locks of Kościuszko’s hair displayed outside Robinson Auditorium ahead of the Monday unveiling.

“That would absolutely be something that we would test for — if there are any ashes,” West Point archeologist Paul Hudson — who was tasked with opening the cabinet-sized strong box that seemed to have suffered water damage from a tear at its bottom — told The Post.

He added that a full-on analysis of the “possibility” would take about a year.

Experts from the archive also explained that Kościuszko returned to Poland before his death in 1817, further complicating the mystery.

“People do spread ashes in different places. It is possible there are ashes or part of his remains [inside the box],” added Hudson.

Voigtschild was hopeful the box contained uniform artifacts, a cadet manual from that time and a medallion of Kościuszko that Thayer was having made in Europe to arrive at West Point some time around 1829.

The academy has a rather underwhelming version of such a medal — Dr. Thomas Frankie of the museum thought what’s in their possession could have been a design mock-up for a much more captivating honor preserved within the capsule for two centuries.

West Point’s monument to Kościuszko — who called the Hudson Valley fortress home from 1778 to 1780 — was a passion project of the cadets at the time.

It was reported that many of them dipped into their own pockets for the $5,000 marvel and took out ads in newspapers to seek a builder.

Charles Petigru was handpicked by fellow cadet committee members, including Robert E. Lee, to deliver a speech at the monument’s dedication on July 4, 1828.

But Petigru was serving disciplinary action at the time for “absenting himself from the parade ground” — and West Point brass wouldn’t allow the speech to be given, according to the archives.

Was an empty box put into the monument as a prank or revenge, or were the contents stolen?

“We’ll have to think about that,” Voigtschild said.