Rare stamp used on absentee ballot.

[82Rigger]

An election official in Broward County, Florida, spotted the rare stamp while reviewing absentee ballots during the US midterm elections last Tuesday.

As a childhood stamp collector, John Rodstrom's eye was drawn to a group of old stamps stuck to one of the forms. At the center of a small, red one was an image of a WW1 bi-plane, but what excited him was that the plane was upside down - an "inverted Jenny" - one of America's most rare and valuable stamps. Only 100 were distributed, after a printing error in 1918.

The stamp had been postmarked, which will halve its value. But others will have to wait to share Mr Rodstrom's excitement. The envelope was placed in a sealed ballot box, which by law can not be opened until September 2008.

Uncancelled, the stamp would have been worth about $200,000.