Sequel to "The Mysterious Card", in which the mystery of the card is resolved.
According to Uncertain Endings: The World's Greatest Unsolved Mystery Stories by Otto Penzler (Penguin Books, 2006), this 2-part story is one of the two most famous riddle stories of all time, the other being "The Lady, or the Tiger?" by Frank Stockton. The Mysterious Card stories were published in a magazine called The Black Cat, the first part in 1895 and the conclusion in 1896.
The magazine publisher in 1912 put the two parts together in one volume, with the second part sealed, and offered a refund to purchasers if they could return the book with the seal still unbroken. We don't know if anyone actually returned the book without reading the second part.