In an invert error, the center image is printed upside-down relative to the frame. Miller liked to tell how he bought one of the “Jenny” airmail inverts of 1918.
“A small Washington dealer conceived a desire to buy a sheet of this issue,” he told the Milwaukee Journal. “He took his $24 and went to the treasury and bought a sheet.”
“When the dealer got back to his shop,” he continued, “he discovered that the airplane was upside down... Packing his grip he went to Philadelphia where he sold the sheet to a large dealer.” Miller added, “I got in early and bought one for $250 and commission.”