Marietta art gallery owner Shae Avery jumped at a request to restore a Rembrandt.

It was the chance of a 38-year career to work on a painting that could sell for millions.

After buying it for less than $100,000 at an estate sale in Virginia four years ago, investors asked Avery to restore the painting.

They had followed a story that circulated for years in their town about an aging art collector and his Rembrandt. After the man died, the group bought the painting and turned to Avery for help.

After looking at the portrait, the art dealer determined the 23-by-19-inch painting wasn’t a Rembrandt. The good news? He said the painting of a bearded man wearing a jaunty, black hat is probably a self-portrait by Peter Paul Rubens.

“I am very impressed with the beard. It really looks like Rubens’ work,” Avery said. “When we got it, it was so dark and dirty you couldn’t tell what it was.”

The investors don’t want to be named because of their mistake. Avery said they are embarrassed even though they will probably still profit handsomely. Avery said the job of authenticating the portrait as a Rubens will fall to the person who buys the portrait.

Larry Shutts, associate conservator of paintings at the Atlanta Art Conservation Center, said it takes years of research and analysis to verify a painting’s provenance.

He said without a proven history, it’s hard to put a name or date on a painting.

“Buying a diamond in the rough is a risky buy, but the potential reward is outstanding,” Shutts said. “These deals are hard to find, but things are squirreled away in basements and attics waiting to be found.”

Even if it’s not a Rembrandt, Avery said the work is the most valuable he has helped restore. He said X-rays revealed the painting’s age — he believes it was done in the early 1600s — and fragility. He added stretcher bars and strength by attaching another canvas behind the painting before removing layers of dirt and paint from a previous restoration effort.

Portrait artist Damon Carter did the finishing touches, replacing chipped paint in the background and fine tuning the beard and eyes. He completed his part of the restoration Saturday.

“This is not the typical, everyday kind of work,” Avery said. “I’m delighted I got a chance to be involved.”