"It was only in the past few months that the owner decided to see if the ring had any value and asked Sotheby's to appraise it," the item description stated. "Much to the owner's surprise, the ring turned out to be a genuine cushion-shaped diamond weighing 26.29 carats with an attractive color grade of I and impressive clarity grade of VVS2."
Sotheby's initially estimated the ring was worth $325,000 to $456,000, but it ultimately sold for a total of $847,667.
The identity of the buyer was not revealed, but the auction house said it was purchased as international trade within the industry, and not by a private collector.
Managing director of 77 Diamonds, Tobias Kormind, said the ring may ultimately be worth far more than its auction price.
"The new owner is likely to re-cut it into a modern diamond that will emit even more sparkle and potentially be worth a multiple of today's price," Kormind said. "I'm convinced the [$13] ring was once owned by royalty or a person of great wealth, because it originates from the 1800s -- before the discovery of modern diamond mines and a time when very few diamonds were available."
