(CNN) -- An intimate black-and-white photograph of Princess Diana as a teenager sold Friday for $18,396, a New Hampshire auction company said.
The photograph -- which may never before have been seen by the public, RR Auction says -- offers a glimpse of the future wife of Prince Charles lying down, perhaps on a bed, wearing a light sweater or top. Only her head and arms can be seen. Behind her a young man leans against the wall, reading, his book resting on her shoulder.
The future princess looks relaxed, half smiling at the camera. A bottle of whiskey can be seen on the windowsill.
Another man is half seen in the foreground, but there is no clue as to who he or Diana's other companion might be.
Large, black wording across the top of the photograph states "Not to be published," and there are two dark lines under the words and above Diana's head. A lighter circle encompasses the words, Diana and the man reading the book.
The only indication of date is a stamp on the back of the print saying 26 February 1981, two days after the engagement of Diana, then 19, and Prince Charles was announced by Buckingham Palace. They married in July of that year.
The photograph likely was taken a year or two earlier.
CNN's Joseph Netto and Laura Smith-Spark contributed to this report.