In early 2011, Bob Ketterer’s phone started to ring — and ring. The callers, what seemed like hundreds of them, all had the same thing to say.

“You’re up there hanging on the wall. You look just like him.”

Ketterer, an 82-year-old retired electrician, had no idea what they were talking about. He drove uptown to the Art Museum of Greater Lafayette and walked up to its second floor gallery, where a widely advertised new exhibit was being shown.

In the center of the gallery, a painting hung high above the ground, towering over him with its bright yellows and blues popping in the gallery lights. In it, a man sat by the light of a window, a planing board in his hands, carpenter’s tools hanging on metal hooks behind him and containers scattered on a nearby desk. The left corner was swathed in sunlight, and the workshop turned to white, then brown, then shadow-black in the soft gradients of a brushstroke. When Ketterer saw the man staring back at him with those translucent blue eyes — deep-set, aged, sad — he felt it immediately.

He went home and, with the encouragement of his brothers and sisters, unearthed some family photographs, relics of his forebears. The painting was the centerpiece of the museum’s exhibit, but the museum knew almost nothing about it. The biggest question of all: Who is the carpenter?

Ketterer believed he had an answer.

In Lafayette, a midsize Indiana town about an hour’s drive northwest of Indianapolis, a small group of artists, historians and longtime residents have been searching for the same man for seven decades. No one knows where he was from, where he lived or when he died. No one even knows his name, at least not for sure. The only known fact about the old carpenter is that a German nun named Mary Rufinia Klocke painted him sitting in a workshop, tools in his hands, eyes gazing to the far side of the room.

The piece is one of Lafayette’s most prized possessions.

With The Old Carpenter, Rufinia did for the 1930s industrial Midwest what Grant Wood did for America’s breadbasket in American Gothic — portray an entire way of life through its vivid archetype. Rufinia was a protégé of the Indiana painter Wayman Adams, a member of the Hoosier Group: an influential generation of Impressionist painters from Indiana who helped push landscape and portrait painting into the mid-20th century. But The Old Carpenter stands alone as what experts consider her greatest portrait.

Records from the 1930s and ’40s are filled with holes and inconsistencies. How she knew her subject, whether he lived in Lafayette or if he existed at all is up for debate. A few have suggested the old carpenter was a figment of Rufinia’s imagination.

Lafayette was once a crossroads. Its Wabash River connects it to a canal system that spanned from New York to New Orleans. And when the railroads antiquated the riverboats, Lafayette became a thriving trading post of drifters and businessmen, laborers and artists. For many in this working-class area — home of Purdue University, three Walmarts and several large factories — he’s the most tangible reminder of a nobler, simpler time. The Old Carpenter, not unlike the immortalized black-and-white photographs of Walker Evans, has become an artifact of Americana.

Those who search for him say he was the man everyone knew, who came as another outsider but was embraced because he could make things — chairs, toys, houses, tools. He was a craftsman, a Midwesterner, a quintessential Lafayette man.

And he is lost.

In 2010, the Lafayette Journal & Courier published the following message: “Michael Atwell, curator of the Art Museum of Greater Lafayette, is hopeful someone can identify the subject of [Rufinia’s] painting, Old Carpenter, in the museum in time for the 2011 exhibit.”

Rufinia emigrated from Germany to the U.S. and ended up at the St. Elizabeth Hospital in Lafayette in 1906, where she worked as a nurse. In 1920, after trying to lift a large patient onto a bed, she suffered a debilitating back injury and gradually took up painting. The Sisters of St. Francis encouraged her work and sent her to art schools around the country.

The local museum owned only a few of her paintings, so to prepare for an ambitious retrospective of Rufinia’s art, the museum solicited loans of her other works from the community and sought to identify once and for all the subject of her most famous piece.

Several people came to Atwell claiming to be the carpenter’s descendents. They told anecdotes of their carpenter relatives and hauled in old tools and photographs. The museum staff was unconvinced. Every carpenter in the 1930s had those tools. The exhibit went ahead with an unnamed carpenter, and it seemed like that was the last time anyone would care about him until Bob Ketterer gazed up at those sad blue eyes that looked so much like his own.

Last summer, a Journal & Courier reader named Katie Klimaszewski sent me an email to tell me she knows who the old carpenter is. She said he was probably a contractor by the name of Stephen Ketterer who helped build the St. Elizabeth chapel when Rufinia was teaching there.

She said her friend’s brother, Bob, Stephen Ketterer’s grandson, tried to tell this to the museum, offering photos and tools to buttress the story. But the curators turned him away just as they’d rebuffed everyone else. Klimaszewski didn’t think the museum gave the Ketterers a fair shake and asked me if I’d look into the story.

I was intrigued. I wanted to know who exactly was in contention for the old carpenter title, and whether there was any way to prove one of them correct. So I asked the staff at the museum to let me see their Rufinia file. Maybe somebody from the outside, with fresh eyes, could solve this mystery.

Atwell told me the only physical evidence — Depression-era carpenter’s tools — proved nothing. Old photographs didn’t prove anything either. In Indiana, a lot of grandfathers resemble an old, white gentleman.

Atwell surmised the man must have been wealthy enough to commission a painting by a well-known local artist. The most likely candidate, he said, was an industrialist named Edwin R. Clegg.

Any art archivist will tell you the place to start learning about a painting is its backside. That’s where you’ll find the provenance sheet, a document that states when and where the painting resided since its creation. But the only thing The Old Carpenter’s provenance sheet reveals is that in 1960, Clegg’s son, Harold, donated the painting to the museum on behalf of the Sister Rufinia Art Club. There’s a donation receipt corroborating this.

It was a no-nonsense argument. During Rufinia’s time, only people with money had portraits done. So just look at who owned the painting, and there you have it: It must have been Ed.

One of Rufinia’s last students, John Oilar, told me Ed Clegg is his best guess, too. (The Cleggs and the Oilars are distant relatives.) Clegg was a co-founder of the Peerless Wire Goods company and a member of the county council, but Oilar thinks Clegg could have had a workshop and crafted furniture as a hobby.

There’s a problem, though. Ed Clegg looks nothing like the old carpenter. Sure, he had deep-set eyes and a white mustache, but the resemblance stops there. The old carpenter’s face is too long, his cheekbones too narrow. And Rufinia wasn’t one to invoke artistic license. In fact, she may have considered it blasphemous to embellish what God made. In nature, she wrote in a memoir, “I find small imitation of the One who made them. It is my sincere wish to reproduce, at least in a miniature way, something of the world around me.”

So why would she paint a prominent businessman and civic leader to look like someone else?

The art museum’s current curator, Michael Crowthers, is a young yet professorial man. On a recent fall afternoon, he tapped a code into a large steel door on the second-floor gallery. He leaned back to tug the handle, revealing a collections room with no windows, high ceilings and a futuristic humming sound. “That’s the temperature control AC that you hear.”

The Old Carpenter was leaned against a shelf on the ground in the back corner. Crowthers crouched down close to the four-foot-tall painting and gestured at Rufinia’s precise brushstrokes. The reason so many are drawn to the painting, he said, is how generic it actually is, how anyone can mold their own lives and histories onto this canvas.

“We had different people bring in these old tools, but, I mean, how many carpenters were there living in Lafayette back then? This could have been anyone,” Crowthers said. “She could have painted this from her imagination. She could have painted this based on someone else’s photograph or painting. You just don’t know.”

I spoke to many of Rufinia’s last students to see if they remembered anything. They recalled the nun’s stern German accent, her wobbling gait, the snack stand and tiny bedroom she had inside her classroom studio. The Art Museum of Greater Lafayette’s executive director, Kendall Smith, remembers learning ceramics and oils from her as a teenager.

“She had a sign on her studio that said, ‘Stop. Look. See,’” he said. “That’s what I think she inspired people to do. You learn to see things that you’d normally walk by and don’t pay attention to. When you discover something new that’s always been there, it inspires.”

But her students knew almost nothing about The Old Carpenter.

My first real clue came months later. An assistant at the museum found a photograph someone brought in back in 2011. It was a grainy, sepia picture of two men posing near a shed. One of them, sure enough, had the signature hat, blue-collar attire and white mustache. This Mysterious Sepia Man was an intriguing second candidate. But that was before I met Bob Ketterer.

Ketterer’s home creaks with history. The two-story house, nestled off a main thoroughfare on the south side of Lafayette, has dark cabinets in the kitchen lined with deeply contoured oak, its creases as storied and personal as the wrinkles of an old person’s hands. Walk down the kitchen aisle and the wooden floorboards groan. The house sounds alive. Ketterer built it himself.

Ketterer has worked as an electrician for more than 60 years in Lafayette. His father was a plumber. His brothers are plumbers, bricklayers and carpenters, which means that each Ketterer home has the touch of family. If you’re a Ketterer in Lafayette, then Bob wired your house. In his own house, he hand-crafted all of its interior wood.

One night, he invited me to sit down at the kitchen table and opened a green, spiral-bound album filled with yellowed photographs. There he was, his grandfather: Stephen Ketterer. Ostensibly, he shares the old carpenter’s features — aquiline nose, thick white mustache.

Stephen Ketterer was born Dec. 12, 1863, in Baden-Baden, Germany, one of 11 children. He left home at 17 to seek prosperity in the United States, landing in 1880 and finding his way to Lafayette, Indiana. There he became a carpenter and worked on the chapel at St. Elizabeth Hospital. Surely the two German Catholic immigrants working at the hospital formed a friendship, Ketterer believes.

The painting, then, could have been a token of friendship. That’s the story he told the museum staff. Ketterer shook his head. “They didn’t believe me,” he said. They said Stephen Ketterer would have been too poor to afford a commissioned portrait. They shrugged, and thanked him for his story.

“This is what I don’t understand,” Ketterer said. “How much money would a carpenter have anyways?” Bob’s daughter, Kathy, argued that a nun wouldn’t have cared about money. She painted The Old Carpenter because she found a kindred soul far from home, a fellow immigrant with a vocation to create. To the Ketterers, The Old Carpenter is a gift to their ancestor, a gift to his posterity.

“Stephen came to America to make his fortune,” said Mabel Ketterer, Bob’s wife. “I guess he never made it. But he made this big family.”

Like the museum, I wasn’t satisfied with the Ketterers’ story, however compelling. There must be hard evidence. But I seemed at an impasse. All I had were stories and pictures of a local celebrity, a Mysterious Sepia Man and a German immigrant. What was I to do?

Facial-recognition technology is an emerging field of study in biometrics. Initially developed for real-life subjects, art historians have explored its application on painted faces. Scientists have said it could help identify The Girl with the Pearl Earring and Frans Hals’ equally elusive The Laughing Cavalier. It turns out there’s someone at Purdue University who studies facial recognition, a biometrics expert named Stephen Elliott. I reached out to him, and he responded with enthusiasm.

There were no surviving Cleggs to collaborate, however. (Harold’s only son, Jerry, committed suicide nearly 50 years ago.) But the Ketterers loved the idea. Finally, scientific proof.

The International Center for Biometric Research is a tidy cluster of computers tucked away on the third floor of a Purdue academic hall. Through the lab’s glass panes you can usually see young engineers munching on pizza and takeout, waiting as scan results come through.

I submitted photos of Stephen Ketterer, Bob Ketterer, Ed Clegg and the Mysterious Sepia Man, and a technician fed them through a facial-recognition program called MegaMatcher. It analyzes such data as the distance between the eyes, ears and nose.

The computer began to spit out numbers on an Excel spreadsheet. One of Elliott’s assistants looked at the computer monitor and began to explain the algorithm. I was expecting percentage points of probability, or maybe a blinking green alert: “Match! Match!” Instead, these lists of numbers would need to be interpreted.

The answer seemed so close. Just tell me who the old carpenter is, I thought.

My search for the old carpenter took me from the home of Rufinia’s student, John Oilar, in Crawfordsville (an old stop on the Underground Railroad, where runaway slaves once sheltered in the attic), to the Hoosier Salon Art Gallery in Carmel, a definitive showcase for Indiana artists since 1925. One of those was Rufinia.

Several newspapers back then mentioned Rufinia won a prestigious regional award in 1936 from the Hoosier Salon for a painting called His Work Shop.

Though The Old Carpenter is dated 1940, Crowthers said it was likely painted earlier and may have been known as His Work Shop. He suggested I check out the Hoosier Salon — it might have an old catalog with more information.

Despite multiple reports in the Lafayette art museum’s file of a 1936 His Work Shop, the Hoosier Salon itself has no record of any such painting. That wouldn’t be so surprising (since art records in the 1930s are generally spotty) if the gallery didn’t keep such meticulous records. In fact, executive director Donnae Dole took an independent look at the records and came up with the same conclusion: From 1927 until 1959, Rufinia had 36 works of art juried into the Hoosier Salon’s annual exhibition, and none of them are called His Work Shop or The Old Carpenter.

In 1936, Rufinia did win an art award from the Hoosier Salon. It’s for a still life called Mixed Bouquet. She won another award in 1937 for a painting called Old Cunning, but if this was the painting then why would it be one year off with a different name? Why would the Hoosier Salon have records of all of Rufinia’s award-winning paintings except for the most famous one of all?

The scraps of information from St. Elizabeth, the library, the museum, the historical society, the literature on Rufinia and newspaper articles form a thick volume — but it’s filled with problems. I wondered if a clear picture would ever emerge.

Back in the lab, Stephen Elliott peered at the results of our facial scan. He stood up from our huddle around the computer, stretched his arms out and patted me on the back.

“Sorry, mate. No luck. A good try, though.”

“Wait, what?”

He said the threshold was too low to offer any satisfactory match.

To explain, Elliott led me back to the entrance of the lab and placed his hand on a security scanner at the door, which clicked open. Elliott is missing a ring finger, so he can’t give the scanner very good information. He has what is considered a low threshold for a match. “You can put a textbook over the scanner and it’ll think it’s me,” he said. He wasn’t lying. When I put my hand on it, the door opened. If it weren’t for a second layer of security — a PIN — anyone could waltz into the lab as Stephen Elliott.

For facial recognition to work, the elements have to be just right. The face needs to be straight-on, with even light distribution. Hats and glasses are tricky, but not necessarily damning.

The Old Carpenter was too difficult to scan. The brushstrokes, the hat, the contrast between light on the left side of his face and dark shadows on the right meant the computer couldn’t get a good read. Combine that with the graininess of Mysterious Sepia Man and the tilt of Stephen Ketterer’s head, and the computer ended up just like us: stumped.

The unsolved mystery has frustrated the Lafayette community. But all the questions have kept people interested in The Old Carpenter.

And perhaps there are more leads to follow — other family stories about a grandfather who befriended a nun. Maybe that’s the true story. The library’s city directories from 1935 have Stephen Ketterer listed as a carpenter, along with Harry T. Ford, Clark Horlacher, Jos Siegfried, Harvey Lock, Edward Hilburn and others. These are just some of the men who could have found a kindred spirit in Mary Rufinia Klocke, sat for her in his workshop and gazed ahead.

“This all reminds me of a book that I have about the Lincoln assassination,” said Kevin Cullen, a local writer and historian. “It includes several photos of dead, bearded men of the Civil War period. Each is supposedly Lincoln in death. Some of the men look like Lincoln, some kind of do, but others bear no resemblance. Regardless, to the families that own the photos, each one is Lincoln, because they want it to be.”

“We have no reason to make a crazy claim,” said Ted Michalke, one of Bob Ketterer’s nephews. “But, whether it was him or some other immigrant who had a connection to the sister, it’s still significant to us as a family, if it literally was our grandfather, or just a representation of everything he meant in his life.”

Though The Old Carpenter is the art mystery of the century for Lafayette, it was nothing of the sort for Ketterer. He knew at first glance who the old man was. There are few things he’s so sure about.

Ketterer had said he hoped I could find the evidence to cement his claims, but when I returned without an answer, he was neither surprised nor disappointed. To him, there was never any mystery. That night I visited him, he was sitting in a temple to Stephen Ketterer’s heritage — a home crafted from the ground up, built with wood that was cut, sanded and polished by Ketterer hands.

Bob Ketterer looked around his home. The Old Carpenter was everywhere.