Jack the Ripper postcard auctioned for nearly $30,000

May 1 (UPI) -- A postcard believed to have been sent to London police by serial killer Jack the Ripper sold at a British auction for nearly $30,000.

Grand Auctions of Folkstone, Kent, England, said the 2.75-inch by 4.75-inch postcard sold for $29,914 when it went under the hammer on Monday.

Jonathan Riley of Grand Auctions said the card was won by a British private collector at the end of a bidding war with a U.S. party.

Riley told the BBC the auction shows "how much interest in the Ripper there still is."

The identity of Jack the Ripper, a serial killer responsible for the deaths of at least five women in the Whitechapel area of London between August and November 1888, remains a mystery to this day. Several letters and postcards received by police were signed "Jack the Ripper," but investigators only believe a select few to be authentic.

The postcard sold at Monday's auction was dated Oct. 29, 1888, 11 days before the death of Mary Kelly, believed to be the killer's final victim.

"Beware there is two women I want here and I mean to have them my knife is still in good order it is a students knife and I hope you liked the kidney," the message reads. "I am Jack the Ripper."

The auctioneer said the postcard had been kept in police files before being given to a retiring police constable in 1966. The constable's widow brought the postcard to Grand Auctions, where it had been expected to fetch $816-$1,224 before it sold for nearly $30,000 on Monday.