66, began when no one at a government printing plant in Washington noticed the problem with the planes appearing upside down on a single sheet of 100 stamps among thousands printed in May 1918. Who made off with the block, and who separated them into single stamps, remains a mystery. It had been one in a block of four that belonged to the daughter of one of the founders of Dow Jones & Company. 76 was stolen at a stamp show in Norfolk, Va., in 1955. 28 for $389,000, both in February of last year, and No. Three that had small flaws have changed hands since then, for far less money: No. 58 sold for $1.35 million in May 2016, according to the Siegel website. Inverted Jennies are not the most expensive stamps in the world - that title belongs to the one-cent magenta from British Guiana, the only one of which sold for $9.5 million in 2014. A great-uncle apparently bought it after the sheet of 100 was broken up, and after the great-uncle died, the great-aunt left it to the man’s mother in the 1930s. Lyons said the Illinois man’s 91-year-old father had been a stamp collector, but the stamp had come from his mother’s side of the family. 49 has been a black hole on a Jenny website set up by Siegel Auction Galleries, a Manhattan firm that has sold many Jennies over the years. A 1986 book that tracked each of the 100 Jennies had this entry for No. 49 remained off the radar, to use an expression that did not come along until decades after the Jennies had captured the public’s imagination. Lyons suspects the man is considering selling it. Most of all, it was never resold, although Mr. It was never put in a locket, as still another was, as a present for an owner’s wife. It was never sucked up by a vacuum cleaner, as another was. It was never recut and reperforated, as one Inverted Jenny was after it was stolen. It never had a gummed hinge affixed to the back, for mounting in a stamp album. The man in Illinois said the stamp had been in his family for generations, most of the time in one safe deposit box or another. Lyons, the foundation’s executive director, called.