Stamp investors fought hard over a rare CIA Invert at HR Harmer's spring sale earlier this month.
The 1979 inverted $1 Rush Lamp, one of only 95 known to exist, made $19,000 at the US auction, far surpassing its $15,000 low side estimate.
It continues a tradition of high prices for these specimens. A block of four CIA Inverts sold for $60,000 in 2004.
Featuring a lamp holder and text that is inverted relative to the flame in the corner of the stamp, it was the first major invert error since the 1962 Dag Hammarskjöld.
The stamp takes its name from the CIA employee who bought a sheet of the stamps from a post office.
Staying with upside down stamps, a 294a Pan American Invert also performed well at the sale, comfortably beating its low end estimate with a $5,500 showing.