ELLSWORTH – The elegant brick mansion on West Main Road is filled with family heirlooms, fine furnishings and artwork that offer glimpses into what it was like to be a member of one of the area’s most prestigious families.

But one of those items is posing new questions to the staff of the Woodlawn Museum. The piece is small in size but big on mystery.

Over the past few years, staff at the museum, also known as The Black House, have been cataloging the estate’s extensive collections. They recently discovered that what they thought was a black-and-white photograph of former resident George Nixon Black Jr. was not what it appeared to be.

The image was a photo of a painting of Black, a painting that is nowhere to be found.

Not only are Woodlawn staff now searching for the original piece of art, they also are hunting for more information about its creator.

“Maybe it got damaged, and maybe it got thrown away,” said Rosamond Rae, Woodlawn’s collections manager. “Sometimes these things find their way into auctions. We just don’t know.”

The framed photo shows Black, grandson of Col. John Black, who gained riches in the lumber business and built Woodlawn between 1824 and 1827. It sits on top of a chest at the head of an elliptical staircase in the mansion.

Black, a Bostonian who summered in Ellsworth, inherited Woodlawn in 1880 and willed it to the Hancock County Trustees of Public Reservations upon his death in 1928. He was the last member of his family to live in the home. It contains all of its original furnishings and has been open to the public since 1930.

Upon closer inspection, Rae said, staff members noticed something else in the photo.

“When we looked very, very closely, we could see the signature of the artist,” she said.

That artist is Charlotte Otto Shetter, a largely unknown although prolific painter who lived most of her life in New York.

Black and Shetter were apparently friends. In 1917, Black amended his will to include her. He gave her $25,000, less than he gave to his dearest friends but more than he gave to some of his cousins. Her name also appears in the wills of Black’s closest friends.

That leads researchers, such as Rae and Jane Goodrich of Swans Island, to wonder about the relationship between the two. Both women doubt there were romantic ties between Black and Shetter, neither of whom were married. But they say the relationship is intriguing and could offer information about the lives of both people.

By the museum staff’s best guess, the portrait was made between 1916 and 1928, when Black was in his 60s. Its value depends on its size, its condition and its history of ownership, all of which are unknown at this point, Rae said.

“The value to us would be priceless,” she said.

Goodrich said she suspects the painting is still in the area, in someone’s basement or attic, perhaps taken down from the wall for repairs and forgotten.

“Where is it? Why was it done?” she said. “There must be someone who knows.”

Goodrich began researching Black after moving into and re-creating his former home, Kragsyde, a well-known shingle-style summer cottage on Swans Island. Her research led to Shetter, a Brooklyn-born artist who had studios in Greenwich Village in New York City and elsewhere. She created many paintings, including one she exhibited at the National Academy of Design in New York City and another she exhibited just five years before her death in 1957. She was in her 90s when she died at a nursing home in Connecticut.

Shetter said she has never laid eyes on even one of those pieces.

“It is absolutely impossible that her paintings don’t exist,” she said. “Her paintings have to be somewhere. There is somebody who is going to know who she is.”

The museum will make an appeal to its members for information about the painting in its next newsletter, which will be mailed to about 300 households.

Joshua Campbell Torrance, executive director at the museum, hopes that will generate some leads. Anyone with information about the painting or the artist may call the museum at 667-8671.

“We are very much looking to connect with the person who might know something about this painting,” he said.