WESTBROOK — When City Clerk Lynda Adams searched through newspaper archives for information about the city’s 1914 centennial celebration, she didn’t see much written about what went into the time capsule buried in Riverbank Park.

“We didn’t know what was in the box. That’s what led to the whole excitement,” Adams said about the buildup before unsealing it last spring.

The city’s Bicentennial Committee decided it wants Westbrook residents 100 years from now to have the same experience. So, aside from some documents and keepsakes, members are not telling what’s going into the time capsule that will be sealed Tuesday evening during a ceremony at the Westbrook Historical Society – the last event commemorating the city’s 200th birthday.

“That’s one of the things we liked – the mysterious part, the mystique of it,” said Adams, who chairs the seven-member committee.

She’s gone to some length to make sure most of the contents of the box stay under wraps until it’s set to be opened in June 2114. She even destroyed the electronic file containing the minutes from the committee’s meetings where members discussed what to put in the time capsule, placing the only paper copy inside.

Asked whether that was legal, she smirked and shrugged. Thursday’s her last day as city clerk, anyway.

The committee has taken the task of putting together the time capsule seriously because it was evident what effort went into the same process a century ago.

The 100-year-old capsule was protected so well that even with modern equipment, getting to it was a painstaking process – much beyond the hours it took the Boston Museum of Fine Arts conservator last week to release the recently discovered time capsule buried in the Massachusetts Statehouse by Paul Revere and Samuel Adams in 1795.

Westbrook city staff first unearthed the granite stone marking the time capsule and its 5-foot cement footing a year ago.

Not knowing whether the box was inside the stone or the cement base, employees in the Public Services Department started off trying to separate the two pieces with a jackhammer, said Arty Ledoux, the department’s deputy director and a member of the Bicentennial Committee.

As they hit cavities in the stone, they worried about striking the time capsule itself, he said. So the city brought in the Portland Police Department’s bomb squad to screen the monument to try to visually locate the box inside. The equipment, however, couldn’t penetrate the stone.

Next, they solicited the expertise of a monument company owner, who said it seemed the granite stone was made of two pieces sealed together.

After some careful chipping, it separated, revealing the box inside, which had to be removed with a pry bar.

Among the items inside were postcards with pictures of the city, pins worn by members of the centennial committee, a Westbrook Congregational Church directory and – a favorite of the current committee members – a program from the city’s Board of Trade annual banquet with a menu including oysters on the deep shell and baked chicken halibut.

In deciding what to put into the new time capsule, Adams said, the committee wanted to include items that may be obsolete in 100 years, like postage stamps and a phone book.

There are newspaper articles on plans for ongoing projects in the city, like the Public Services Building approved by voters in June, to show future Westbrook residents the origins of city amenities that, by then, will be historic.

As for the items that the committee won’t reveal, Adams would only say that some could be very valuable by the time they’re unveiled.

At the event Tuesday, starting with an open house at 6 p.m. followed by a ceremony at 7 p.m., the contents of the 100-year-old time capsule will be on display and Adams will talk about the city’s history before sealing the new capsule shut.

The event also will honor Ellie Saunders, a descendant of the city’s first settlers and a founder of the Westbrook Historical Society, who died Nov. 22 at the age of 94.

If it hadn’t been for Saunders, the city may have missed the date set 100 years ago for opening the time capsule.

Instructions to open the stone on June 9, 2014, were written on a plaque on the monument that has sat for a century in Riverbank Park. But over time, the stone, which sat close to the ground, had become obscured by the surrounding landscaping.

To public services employees, it was just one of many monuments in the city that they work around.

“You look at it so often, after a while you don’t see it,” Ledoux said.

But Saunders, who was the first person to bring the 200th anniversary of the city to Adams’ attention, also made the clerk aware that there was a time capsule waiting to be dug up.

This time around, the city plans to put the monument in a more prominent location in the park and raise it higher off the ground, so there’s no chance of overlooking it.

After the box is sealed Tuesday, it will be placed inside another box that will be welded shut and buried sometime in the spring.

Adams isn’t too concerned about how the tricentennial committee will get it open.

“They didn’t make it easy for us,” she said.