The brightly colored painting, attributed to Sol LeWitt, on the wall of 644 Pacific St. in Brooklyn won’t be around too much longer. The building is slated to be leveled to make way for the Atlantic Yards development. But the questions the painting raises about the artistic practice of LeWitt, the conceptual artist who died last month at 78, may be discussed long after the building comes down.

Like all of LeWitt’s wall drawings — a term of art that encompasses paintings as well as drawings — the painting at 644 Pacific St., where two of LeWitt’s assistants, Jo Watanabe and Sachi Cho, used to live and work, has a number, 848, and comes with a signed certificate of authenticity that includes both a verbal description of the painting and a diagram. The certificate, and therefore the painting, belongs to Mr. Watanabe and Ms. Cho, who are married and who worked for LeWitt for almost 15 years.

Wall drawing no. 848 got some attention last month when the group Develop Don’t Destroy Brooklyn, which opposes the Atlantic Yards development, sent out a mass email about the painting’s distinguished legacy and imminent destruction. Even they seemed to recognize, however, that the situation didn’t constitute an artistic tragedy. As an article in the Brooklyn Paper explained, LeWitt, as a conceptual artist, regarded the physical wall drawing as less important than the idea on which it was based. For most of his career, he didn’t execute his wall drawings himself: He came up with the concept, which he expressed in a set of instructions that his assistants carried out. Installations of the wall drawings are often temporary; if they are shown in a museum or gallery exhibition, for instance, they have to be painted over after the exhibition closes. If a collector has a wall drawing installed in his house and he moves, he is supposed to paint it over and then have it reinstalled by approved LeWitt assistants in his new house. In the case of wall drawing no. 848, since Mr. Watanabe and Ms. Cho own it, they are entitled to reinstall it somewhere else.

So the painting at 644 Pacific St. seems unremarkable — a typical example of a practice in which, as anyone who has taken a class on abstract art can tell you, the artist’s concept comes first and is supreme, and the execution by assistants is secondary. Interviews with Mr. Watanabe and Ms. Cho, however, have added a wrinkle to the story behind wall drawing no. 848.

Asked by a reporter whether she had the instructions for the wall drawing, Ms. Cho said there weren’t any, but that there was a diagram. LeWitt did a diagram for the painting? the reporter asked. Ms. Cho paused. Well, he did a diagram afterward, she explained. In fact, she continued, her husband came up with the idea for the painting himself and executed it. When LeWitt saw it, he liked it so much he decided to bless it as one of his own.

Mr. Watanabe, contacted later, expressed irritation that his wife had revealed the incident, but he nonetheless confirmed it. He said he was working on the basis of ideas that LeWitt had laid out, so the question of who initiated this particular work was inconsequential. “If somebody else didn’t initiate the idea [expressed in this painting], then he [i.e., LeWitt] would have,” Mr. Watanabe said. “No element in this particular piece is very different from any other Sol LeWitt. That’s the great thing about Sol’s work. It was not necessarily an individual, a personal thing.”

Mr. Watanabe suggested that the piece evolved out of practice drawings that he himself frequently made on the walls of 644 Pacific St., either to test out new techniques or to train new assistants. In the case of this painting, “It [became] bigger and look[ed] like a true wall drawing,” Mr. Watanabe, whose English is slightly ungrammatical, said. LeWitt “liked it, and he said, ‘I sign certificate and give to you’ — Sachi and myself — ‘as a present.'”

It is impossible to know exactly what happened, and dealers and curators who have worked with LeWitt and were told this story had sharply different reactions. Any blurring of what constitutes an “authentic” Le-Witt would, of course, mean a tremendous headache for the artist’s dealers and his estate — not to mention potential financial loss.

Several individuals declined to comment, instead referring a reporter to LeWitt’s head assistant, Susanna Singer. Ms. Singer is preparing a catalogue raisonné of the wall drawings in collaboration with the Yale University Art Gallery and Yale University Press.

Ms. Singer, who worked as LeWitt’s assistant for three decades, dismissed the story as untrue. “It doesn’t sound like anything he’d do,” she said. “That’s all I can tell you.”

The dealer Paula Cooper also cast doubt on the story, saying it was “not the way Sol worked. No one else made the drawings.” Asked if the story perhaps suggested a more fluid practice, where ideas might have been exchanged, Ms. Cooper said, “Absolutely not. It is so rigorous. Sol was very controlling about the wall drawings.” She added,”I think what you’ve got here is a personal story and you don’t know what really happened.”

Some people, though, thought the story was plausible. “It doesn’t sound entirely far-fetched,” the president of PaceWildenstein, Douglas Baxter, said. LeWitt “had a very generous spirit, and he may have come and liked what they did and said, ‘Yeah, great, this is a Sol LeWitt.'”

Asked whether the story behind wall drawing no. 848, if true, would represent an exception to the conventional way that LeWitt worked, the director of the Barbara Krakow Gallery in Boston, Andrew Witkin, said it wouldn’t, because “there was no one convention.” Mr. Witkin said: “Sol was a very sensitive artist, and his assistants worked very closely with him.” LeWitt would have discussions with his assistants about things he wanted to try and how they would work, Mr. Witkin explained, and assistants might explore these ideas on their own. “People who have collaborated and worked for Sol for a long time understand what he’s going after,” Mr. Witkin said. “You have to get away from past ideas of authorship and solitary artists making works on their own.”

The chief curator at the Hammer Museum in Los Angeles, Gary Garrels, who curated a major LeWitt retrospective at the San Francisco Museum of Modern Art in 2000, seemed to go back and forth about whether the story was plausible. He noted that Le-Witt’s assistants worked with him for a long time, and that the artist was “very open” but also “extremely rigorous and very precise.” In the end, he effectively threw up his hands. “I have no idea,” he said. “As long as he signed a certificate, then however the work was generated, he [LeWitt] accepted it as a Sol LeWitt work.”