RALEIGH, N.C. (AP) — A collector is defending his recent purchase of a century-old photo believed to depict children born as slaves after similar images found online called its rarity into question.

The photo found in a North Carolina attic in April was part of a trove of pictures and documents bought by collector Keya Morgan for $50,000. Morgan and an art historian say they believe the photo depicted two children who were either slaves or just emancipated in the early 1860s.

Since an Associated Press story was published last week about the photo and Morgan’s claims that it was extremely rare, critics have located similar images of the children on eBay and at a digital archive of the New York Public Library. Bloggers and anonymous commenters said the existence of the other images casts doubt on Morgan’s claims that the photo is an original taken around the time the Civil War began.

But the New York collector said his photo was made from the original negative taken of the two children in the 1860s, while the others appear to be poor-quality copies made years later. He said his picture is a wet plate albumen print, which produces rich tones.

Will Stapp, a photographic historian and founding curator of the National Portrait Gallery’s photographs department at the Smithsonian Institution, agreed that Morgan’s photo is made from the original negative, but said he couldn’t determine whether the others were copies made later.

The picture depicts a child identified by writing on an album sleeve as John, barefoot and wearing ragged clothes, perched on a barrel next to another unidentified young companion.

Morgan said he paid $30,000 for the album of photos and $20,000 for a document describing the sale of a slave named John, which Morgan said is connected to the photo.

‘‘If you are buying a Picasso painting, let’s say for $20 million, you have to go to a professional who sells Picassos for an expert opinion not somebody who sells a copy for $10 on eBay,’’ said Morgan, who recently debuted a rare image of entertainer Marilyn Monroe with President John F. Kennedy. ‘‘If anybody understands this, it’s myself.’’

The eBay and library photos were listed as stereoviews, which can look 3D when seen with a viewer, and credited to a photographer named Jerome Nelson Wilson. The eBay image was sold with other photos for less than $200 last week.

Wilson could have obtained the negative for the original or a copy of the negative and made prints from that, Stapp said.

Stapp and Morgan said the photo discovered in North Carolina was created by somebody associated with the photography studio of Mathew Brady, a famous 19th-century photographer known for his portraits of historical figures.

However, Bob Zeller, president of the Center for Civil War Photography, said that it was unlikely that Wilson would have reproduced a Brady picture when there were other Wilson photos in the eBay listing that showed black subjects.

He said that since there were multiple stereoviews attributed to Wilson, it is more likely that he originally took the photo of the two children. Still, Zeller said he couldn’t rule out that a Brady photographer took the shot.

‘‘So, ’Which way did the street go?’ is kind of the question,’’ he said.

An estate petition uncovered in the past week also raises the question of whether the 1854 slave sale document bought by Morgan could refer to someone other than the John in the picture. Morgan’s document details the sale of a slave named John from the estate of George W. Potter.

Potter had died before the sale. The AP located an undated petition by the estate’s administrator, requesting the court’s permission to sell ‘‘a certain negro John aged 27 or 28 years’’ to settle Potter’s debts to ‘‘sundry persons.’’

Given that the John described would have been in his 30s by the time Morgan thinks the photo was taken, there is no way the John in the photo could be the same John mentioned in the petition.

However, Morgan said he still thinks his photo and document are linked, and that there could have been other slaves named John whom the petition was describing.

A search at the North Carolina State Archives turned up no detailed inventory of Potter’s estate, which could have listed if he had more than one slave named John.

Harold Holzer, an author of several books about Lincoln and an administrator at the Metropolitan Museum of Art, he wasn’t sure about the origin of the photo, but that it’s poignant no matter what.

‘‘It’s a powerful image and a beautifully composed image by whoever took it, whenever it was taken,’’ he said.