1795 time capsule unearthed

• NEW: Box will be X-rayed on Sunday before next steps are decided


• Workers fixing a leak at the State House discover nearly 220-year-old time capsule


• Capsule was buried in 1795 by Paul Revere and Sam Adams


• Its contents will be revealed next week

(CNN) -- A time capsule buried by patriots Samuel Adams and Paul Revere more than two centuries ago was unearthed Thursday in Boston.

The box-shaped capsule was placed by the Revolutionary-era duo, along with Massachusetts developer William Scollay, in a cornerstone of the Massachusetts State House in 1795, the year construction began on the building, CNN affiliate WBZ reported. At the time, Adams was the Massachusetts governor.

The box has been taken to Boston's Museum of Fine Arts, where experts will X-ray it Sunday, said Meghan Kelly, spokeswoman for the Massachusetts Executive Office of Administration and Finance.

1795 time capsule unearthed in Boston

"This will give us an idea of what's in there and how well-preserved the contents are," she said. "Once we do that on Sunday, we'll have a better idea of the next steps as far as opening it goes."

The box was found when current-day workers were repairing a water leak. They called in a local expert from the Museum of Fine Arts who spent more than seven hours Thursday delicately and painstakingly chipping away at the cornerstone, trying to extricate the box.

A person from the MFA will chip away at the bottom of this cornerstone to retrieve the time capsule.

— Carl Stevens (@carlwbz) December 11, 2014

"What we know the box contains, based on the notes that we have, is a Paul Revere plate, papers and coins from the 1600s," said Massachusetts Secretary of State William Galvin, who also heads the state's historical commission. "It may contain other stuff, too; we don't know that yet."

Galvin said the capsule's contents are expected to be revealed next week.

"The contents are of concern, but the plaster that held the box in place is in good condition," he said.

After examination, the capsule will probably be returned to the State House, Galvin told WBZ, though a new container will probably be created.

This is not the first time this particular capsule was unearthed, according to Galvin. In 1855, it was dug up during emergency repairs to the State House and put back in place when the cornerstone was reset.

Extra precautions were taken then to ensure the box's safekeeping, among them some coins added to the cornerstone for good luck. They came free during the work Thursday.

A coin that apparently fell out of the time capsule here at the State House.

— Carl Stevens (@carlwbz) December 11, 2014

This is an iPhone picture of the time capsule which is still embedded in the corner stone.

— Carl Stevens (@carlwbz) December 11, 2014

"There were some coins that were tossed in the 1855 ceremony in the mix of the mortar. They are in good condition, so we are optimistic that the box itself has withstood the test of time and that it will therefore be holding the contents securely," Galvin said.

Galvin says both time-capsule events -- in 1795 and in 1855 -- were chronicled in detail and said his office is looking into whether new items from the current era will be added to the box and reburied.

113-year-old time capsule found in Boston

CNN's Carma Hassan contributed to this story.