It happened when Ms. Greene, a labor historian, was directing a survey to locate and preserve records documenting the New York region’s labor history. She would become visibly excited, even flushed, with each discovery, down to a page of a scrapbook pasted with old photographs of smiling bricklayers from a union local in Long Island City.

Such relics provided a spy-hole into the lives of the workers who built New York, and were the kinds of historical documents that Ms. Greene, 59, was seeking five years ago during the survey, which became part of the Robert F. Wagner Labor Archives at New York University.

Despite many fascinating finds, Ms. Greene still had not located any record older than 1881 from the 600 labor organizations that her project surveyed.

Then one day, as the effort was nearing its end, she had a major breakthrough. Cited in the survey was a visit by a researcher in 1984 to the General Society of Mechanics and Tradesmen of the City of New York.

On a hunch, Ms. Greene went to the society’s headquarters on West 44th Street and asked a librarian where their records might be. “In some room upstairs where nobody ever goes,” was the response, Ms. Greene recalled. “As an archivist and historian, I went ‘Bingo!’ ”

In fact, there were three rooms and four safes full of documents. In two of the rooms, handwritten ledgers were stacked to the ceiling. The paper trail led back to the society’s founding in 1785, and Ms. Greene quickly realized that in addition to a historical jackpot, she had gained access to a largely unknown organization.

Visiting the society conjures up thoughts of old wood and forged metal, and unlocks the timeless secrets of money, power, commerce and industry at the heart of the city. The society was established to improve the educational and cultural opportunities for working people. Although in plain sight, the organization’s building at 20 West 44th Street, which also houses a curious lock museum, a library and a free technical school, is a little-known treasure.

A replica of the Parthenon’s marble frieze graces the outside of the stately Beaux-Arts building, across from the Harvard Club. In the lobby, jutting from a wall, are an imposing arm and hammer, an early emblem of the blacksmith’s trade. The hammer is pounding the society’s motto, which is inscribed on hand-painted banners of royal blue and gold on each of the six floors: “By Hammer and Hand All Arts Do Stand.”

Ms. Greene’s enthusiasm for research and her determination to whip things into shape led her to become, just months after her discovery, the society’s historian and director of the library, which was still entering new books into ledgers by hand when she arrived.

“I trusted something good would happen,” Ms. Greene said of her first visit. She is determined to preserve the records and make them more widely accessible. In 2005, the society’s records from 1785 to 1955 were opened to researchers for the first time, through a grant from the National Historic Publications and Records Commission.

From Ms. Greene’s perspective, the records she brought to light are a compelling chronicle of intrigue and industrialization, of New York’s early inventors, the men whose work was integral to the paving of streets and the raising of great buildings. These were established businessmen with a grasp on the levers of power who were equally invested in helping the working man. “It’s a complex industrial past,” Ms. Greene said.

She and a fellow archivist, Gabrielle Sanchez, who worked for the society, listed each item they found in a 53-page document: minutes from committee meetings, library ledgers the size of portrait paintings, civic medals, Civil War banners, and tiny silk flags that once graced the tables at the society’s annual black-tie banquet.

Ms. Greene learned of the tradition to initiate the New Year at the society’s annual meeting, which was open only to members, by reading the minutes from the meeting of 100 years earlier. And then there were the little black and white marbles the society once used for voting. After mentioning them, Ms. Greene put her hand over her mouth, unsure if their revelation was safe for public consumption.

“Each generation writes our own version of history,” Ms. Greene said from behind her giant wooden desk in the library office which is adorned with framed pictures of the society’s previous locations.

On Nov. 17, 1785, the society was born as the General Committee of Mechanics, with 22 men gathered in Walter Heyer’s public-house on Pine Street in Lower Manhattan. What stood out for Ms. Greene about the founders was that their first annual meeting on Jan. 2, 1786, was truly representative of the city’s many trades, including hatters, butchers, sailmakers, bolters and combmakers.

Today, the society has about 200 members, including architects, engineers and owners of construction-related businesses that deal with mold abatement, heating and ventilation.

One of the society’s most fabled and revered members was John M. Mossman, a large bearded man who favored bow ties, was a vault builder and donated the collection that become the lock museum. (“A really good lock needs a really good container,” Ms. Greene explained). He died nearly a century ago, but his collection endures.

The collection consists of more than 370 locks, from the earliest-known Egyptian ones (the wooden keys resemble ancient kitchen implements), that date from 4000 B.C., to modern devices. Exhibit No. 33, a Day and Newell lock made in New York in 1838, was prized as the first unpickable lock. When the key is turned, 83 internal pieces rearrange themselves like pieces of a puzzle, all moving with a single purpose.

Despite the society’s storied history, luxurious location and ornate design, interest is limited mainly to preservationists and the descendants of former members. “We had two major donors,” Ms. Greene said. “Andrew Carnegie in 1904 and Amos F. Eno in 1917.”

But a renaissance seems to be slowly in the making. Old dusty volumes are being taken out of storage and a lecture series on labor and literature is under way.

There are obstacles, though. Ms. Greene says that the archive shelves are not ideal for preservation and that the society’s limited resources do not permit installation of central air-conditioning in the building.

One of Ms. Greene’s more interesting discoveries is a silver-colored safe made in New York in 1842. The heavy doors open easily like an enormous book, each wing features a sculptural relief of a gentleman in top hat and tails, absorbed in a valued tome that rests on a safe while the building behind him is consumed in flames. The blazing image was both an advertisement and a deal clincher for the purchaser, a hard-sale reminder of the security and peace of mind he was investing in.