Michael Winter

USA TODAY

A time capsule buried in 1795 by Paul Revere and Samuel Adams was unearthed Thursday in Boston at the Massachusetts Statehouse, possibly the oldest such U.S. artifact ever uncovered.

About the size of a cigar box, the copper container — green from oxidation and caked in plaster — was found in the cornerstone of the "new" statehouse on Beacon Hill, which was completed in 1798.

As Boston Museum of Fine Arts Conservator Pam Hatchfield chiseled away for hours to free the box, five silver coins spilled from the stone block — measures of good luck tossed in when the capsule was entombed by the revolutionary heroes 219 years ago, officials told the Boston Globe. At the time, Adams was known as the governor, not a beer.

The world will have to wait a little longer to learn what's inside. The museum will X-ray the box over the weekend and reveal its contents next week.

It's the second time the time capsule has seen the light of day. It was dug out in 1855 during emergency repairs to the building, which houses the legislature and governor's offices, and replaced when the cornerstone was reset.

Another bit of hidden history was uncovered in September in the city that practically invented American history. A 113-year-old time capsule was found in the golden lion atop the original state capitol.