(CNN)This photograph of Adolf Hitler embracing a young Jewish girl who he called his "sweetheart" sold for $11,520 this week.
Known as "the Führer's (leader's) child," Rosa Bernile Nienau became very close with Hitler after they met outside his house in 1933, Alexander Historical Auctions, which sold the photograph, said on its website.
Nienau and her mother were in a crowd of people who gathered outside Hitler's home in Bavaria, Germany, to celebrate his birthday. After finding out that the girl shared his birthday of April 20, Hitler was immediately captivated with her.
The two were later photographed by his trusted photographer Heinrich Hoffmann, Alexander Historical Auctions said.
One of the photos was later inscribed by Hitler himself with the words "The dear and (considerate?) Rosa Nienau Adolf Hitler Munich, the 16th June 1933," and delivered to Nienau's mother Karoline in Munich.
The child had a Jewish grandmother, but that didn't stop her from being the Nazi leader's favorite. "Research shows that even early on, Hitler became aware of the girl's Jewish heritage but chose to ignore it, either for personal or propaganda reasons," the auction house said in the description of the item. "However, when Reichminister Martin Bormann discovered her lack of 'pure' German blood, he forbade mother and daughter access to the Berghof."
The two still maintained a close relationship as pen pals, the auction house said, until 1938, when Bormann permanently halted their correspondence. Seventeen of the girl's letters to Hitler and aide Wilhelm Bruckner can be found at the German Federal Archives, Alexander Historical Auctions said.
Rosa Bernile died on October 5, 1949 at the age of 17 in Schwabing Hospital of spinal polio, according to the auction house.
The photo eventually made its way to the United States, and on Tuesday, it was sold by the auction house based in Chesapeake City, Maryland.
"The photograph was consigned to us, but it's really a mystery how it made it to the US," Andreas Kornfeld, the auctions house's vice president of sales told CNN. "Someone owned it in Germany, that's for sure."
The auction house spent months investigating the authenticity of the photo, Kornfeld said, and they believed that the photos could have served as propaganda to paint Hitler as a kind man who loved children.
"Hoffmann was not just Hitler's photographer, he was a great marketer who helped him along his campaign capturing him in many positive ways," Kornfeld said.
This is not the first time the auction house has sold Hitler-related items. In 2017, a telephone owned by Hitler that he used to issue most of his commands during the last two years of World War II sold for $243,000.
Kornfeld said the photo is probably one of the most unique items the auction house has come across, since autographed photographs rarely come with so much history attached.
"I've seen the photo many times before, but I never knew about its history. I was extremely surprised," Kornfeld said.
The auction house will not release the name of the buyer, but Kornfeld told CNN it was an international buyer.