A rare opportunity for stamp investors to purchase a CIA Invert presents itself next month at HR Harmer in New York.

The 1979 inverted $1 Rush Lamp, one of only 95 known to exist, is expected to make close to $20,000 on May 12.

The Scott 1610c features a lamp holder and text that is inverted relative to the flame in the corner of the specimen. It was the first major invert error on a stamp since the 1962 Dag Hammarskjöld.

The CIA Invert: an expensive mistake

It takes its name from the CIA employee who bought a sheet of the stamps from a post office.

A block of four CIA Inverts sold for $60,000 in 2004.

Harmer's auction will also feature a 1927 10c double impression Lindbergh, estimated to achieve between $15,000 and $30,000.