A long-forgotten time capsule at West Point recently discovered inside the base of a monument and believed to have been left by cadets in the late 1820s is expected to be pried open Monday.

The contents of the small lead box could possibly provide a window into the early, more Spartan days of the storied U.S. Military Academy.

It’s not certain exactly when the box was placed in the monument’s marble base or who chose any items inside, though a committee of five cadets that may have been involved with the time capsule included 1829 graduate Robert E. Lee, the future Confederate general.

The box will be opened during a livestreamed event.

“It’s a mystery, right? A mystery of history,” said Jennifer Voigtschild, the academy’s command historian.

The container was discovered in May during restoration to a monument honoring the Revolutionary War hero Thaddeus Kosciuszko. A construction manager made the surprise find and carefully pulled out the hefty box, which is about a cubic foot.

“After I shut the job down and we roped off the area, then I realized, ‘Oh my gosh, what did we find?’” manager Chris Branson said.

Cadets in the 1820s honored Kosciuszko, a Polish military engineer, with a column near where current classes march and play soccer. As an officer of the Continental Army, he designed wartime fortifications at the location along the Hudson River, before the military academy was established there in 1802.

A plaque indicates the monument was erected by the corps of cadets in 1828. Other evidence suggests it wasn’t completed until 1829. That includes a July 1828 letter from a committee of cadets involved in the dedication, including Lee, seeking advice on lettering for the monument.

It’s also possible the capsule dates to 1913, when the Polish clergy and laity of the United States donated a statue of Kosciuszko to sit atop the column. West Point officials, though, think the capsule more likely dates to the late 1820s, well before the academy grew into the sprawling post producing more than 900 Army officers annually.

In the early 19th Century, cadets lived in wooden barracks without running water. Around 40 graduated each year. Sylvanus Thayer, considered the “father of the military academy,” was superintendent in the 1820s.

X-rays indicated there is a box inside the container, but there are few clues whether opening it will produce a historical bounty or a bust reminiscent of Geraldo Rivera’s televised unsealing of Al Capone’s vault in 1986.

There could be monument blueprints, class lists or a message from the cadet committee. There could be everyday military items like uniform buttons or musket balls. There could be papers, a medallion or other items related to Kosciuszko.

“So lot’s of possibilities,” Voigtschild said. “It could be Revolutionary. It could be from the cadets from the time period of the 1820’s. Or both.”

Lee’s involvement with the monument is coming up just as West Point reckons with his legacy. Lee graduated second in his class and later served as superintendent at the academy before he resigned from the U.S. Army to lead Confederate troops during the Civil War.

The academy said in December it would comply with recommendations from a commission to remove honors to Lee and other Confederate officers. The recommendations, which included renaming buildings and removing a portrait of Lee from a library, were part of the military’s broader efforts to confront racial injustice.

A reconstructed and refurbished monument to Kosciuszko is expected to be in place next summer.