Andrew Bullock, from the auction firm Keys in Aylsham in Norfolk, England, said he expects the 4-inch cigar butt to go for about 300 pounds (almost $500), the Daily Mail reported. The auction is scheduled at Keys on Jan. 29.
Churchill smoked the cigar at one of the most difficult times in World War II for Britain. British troops were bogged down in North Africa, the Wehrmacht was at the gates of Leningrad in Russia and the United States had not yet entered the war.
"It was rare for Churchill not to finish a cigar, so it must have been something very urgent in the Cabinet room," Bullock said.
Nellie Goble, a housekeeper at No. 10 Downing St., found the cigar on Aug. 22, 1941, and sent it to a friend.
"Just a small souvenir to remind you at some future date of one of the greatest men that ever lived in England," Goble wrote on stationery from the prime minister's residence.
The friend gave the cigar to her daughter, who has put it up for sale.