It was a midnight ride in 1775 that earned Paul Revere his place in American history. After riding the countryside on horseback warning of a British invasion, the silversmith cast cannons from iron, made gunpowder and printed Massachusetts’s first currency during the Revolutionary War.

Two decades later, the war hero tucked two dozen silver coins and a silver plate engraved with a date — July 4, 1795 — into a leather pouch. That day, Revere and Massachusetts Gov. Samuel Adams placed the pouch under a cornerstone at the Massachusetts State House.

In 1855, the contents were moved into a brass box and reburied.

On Tuesday at Boston’s Museum of Fine Arts, the world got a look at what Revere and Adams thought was worth remembering.

Museum conservator Pam Hatchfield opened the 10-pound box during a news conference, using a porcupine quill and her grandfather’s dental tool to remove each item. The box contained a Massachusetts commonwealth seal, a page from Massachusetts colony records, five folded newspapers, a dozen coins — including a 1652 “pine tree shilling” — and the inscribed silver plate, which still had fingerprints on it, she said.

The silver plate was “probably made by Paul Revere and engraved by him,” museum director Malcolm Rogers said, according to CNN. “That was the treasure at the end.”

The time capsule was first exhumed in 1855, when the items were documented, cleaned and placed into the box. At the time, other items, such as newspapers, were added to the mix, and the box was cemented beneath a granite cornerstone. Historians have since worried the items were ruined by water leaks, the Boston Globe reported.

The box was rediscovered on Dec. 11 during building maintenance. Hatchfield spent seven hours working to remove the time capsule from the stone. Coins, believed to have been tossed on top of the box for good luck, spilled out when as she chiseled away, according to the newspaper. Once the box was freed, it was X-rayed to give conservators a glimpse inside.

The coins included half-cent, one-cent, 10-cent and 25-cent coins. Hatchfield said some of the coins, those cleaned before they were buried, looked brand new. Others were corroded or had newsprint stuck to them.

Hatchfield did not open the newspapers, which experts said appeared to be editions of the Boston Daily and the Boston Traveller. She said paper conservationists will need to determine whether the papers can be unfolded without destroying them.

“It was like brain surgery with history looking down on us,” Rogers said.

Earlier this year, historians uncovered a time capsule from 1901 hidden in the head of a lion statue at the top of Boston’s Old State House. It contained photographs, newspaper clippings and a book. The capsule was returned to the lion’s head with a few new trinkets: letters from journalists covering the event, the latest edition of the same book and an iPhone 5, the Boston Globe reported.

After the items are preserved, they will be put on display in the museum. And, eventually, the time capsule will once again be buried in the State House cornerstone, Galvin said.

Asked whether officials will add new items to the time capsule before putting it back, Galvin told CNN, “The governor has wisely suggested that we might, so we’ll think about it.”