It is a defining image of New York City’s history, one that captured the essence of an era, even if it was, in part, a staged scene. On a warm autumn day in 1932, 11 workmen sat perched on a steel girder at Rockefeller Center, smoking, eating sandwiches and reading the newspaper some 800 feet up in the air. Nearby, a camera’s shutter clicked: think men in overalls and flat caps, and boots dangling above the rooftops of Midtown Manhattan. The moment captured in black and white was both heroic and mundane. It was a triumph for the city in the throes of economic crisis and has become one of the most famous images in the world.

Today is the 80th anniversary of that photograph, and judging by the bumper crop of framed prints that hang in restaurant washrooms in New York alone, the image remains as popular as ever. Since it was published in The New York Herald Tribune, the photograph has been enlarged to fit a poster, shrunk to note card-size and colored in shades of red and blue. (The black-and-white print is available in The New York Times online store.) Stranger mutations exist too: there is a pickup that drives through the city with a sculptural recreation of the photo rising from its bed, and a picture of someone’s Lego reconstruction circulates on the Internet.

“The image has averaged about 100 sales a month over the last 10 years,” said Ken Johnston, director of historical photography for Corbis Images, the stock agency that owns the photograph. “This is extremely high.”

Oddly enough, for such a legendary photograph from such a celebrated city, we don’t know very much about it. We know that it was taken on the 69th floor of the RCA Building (later renamed the GE Building), as construction of the towering Art Deco skyscraper was nearing completion. Beyond that, little is certain. Although the photograph was originally dated Sept. 29, recent discoveries suggest that it was actually taken nine days earlier.

The identities of the men seated on the steel crossbeam are also a mystery. Over the years, countless people have staked claims, Johnston said, but few have had any merit. “So many people say, ‘That was my uncle,’ ” he said. “But no one has ever said anything definitive about who these guys are.”

There has been considerable debate about the author of the photograph too. Eight decades ago, “Lunch Atop a Skyscraper,” as the image is commonly referred to, was published anonymously. Many thought it was the work of the renowned photographer Lewis Hines, but that wasn’t true. In recent years, it has been attributed to a photographer named Charles C. Ebbets. But according to Johnston, Ebbets was one of several photographers atop the RCA Building that day, and he can’t be sure who shot which pictures.

There were other images taken in the sky at Rockefeller Center, few of which bear a photographer’s name. One picture, of workmen napping precariously on the crossbeam (Slide 5), was shot the same day. Another, of two men lighting their cigarettes in front of the Empire State Building’s pinnacle, (Slide 2) was taken several months later.

“It’s very common in old news archives that images are not credited,” Johnston said. “Photographers were thought of as the guys who ran the machine. The camera was considered a documentary tool, not a paintbrush.”

The photograph’s original glass-plate negative — the kind used in cameras before plastic film — is part of the Bettmann Archive, a collection of 11 million historical images owned by Corbis. It is stored in a refrigerated cave in western Pennsylvania, encased in cool limestone bedrock to prevent it from rotting and decaying. Despite efforts to preserve the delicate artifact, the negative has seen better days. Years ago, a bite-size chunk went missing from its upper left-hand corner. Then it was dropped, and the glass splintered into five pieces.

As with many iconic photographs, attempts are under way to piece together the origins of “Lunch Atop a Skyscraper,” the latest of which is a documentary film called “Men at Lunch,” which debuted at the Toronto International Film Festival.

But today, on the photograph’s anniversary, it is easy enough to put aside questions about what we don’t know and appreciate the image for what it is: a fixed part of the story that New York City tells about itself, about industrialization and immigration, resilience and ambition, hard work and high hopes. Eighty years ago today, Franklin D. Roosevelt and Herbert Hoover were competing for the United States presidency. The Great Depression was in full swing, Europe was struggling to recover from World War I and Adolf Hitler was leading the Nazis to power in Germany. With all that going on, what’s better than a sandwich and a smoke, high above the throng?