One of the most famous stamps in U.S. history has turned up on an envelope containing an election ballot. The inverted Jenny stamp, a rare and valuable postage stamp because of its printing error and short run, was used to mail a ballot in Florida.

Florida, like other states, had elections last week. One unlucky (or unmindful) voter postmarked his or her ballot mailing with a treasure. The envelope was received in Fort Lauderdale. A member of the Broward County Canvassing Board identified the stamp and set the envelope aside, once the ballot had been counted, of course.

The envelope had no return address, and the ballot was invalid because it was not signed and did not contain any other proof of the voter's identity. That also meant that the Canvassing Board couldn't return the stamp to its owner. The owner, whoever it is, might not want it back, now that it is postmarked.

The inverted Jenny was a printing mistake made in 1918. Only 100 stamps were printed with the plane upside down. Once the printers noticed the error, they stopped the print run and fixed the image. The resulting inverted Jenny stamps because quite rare. Many experts say that just one of the stamps can be worth up to hundreds of thousands of dollars.

Just last year, a block of four of the stamps sold for $3 million.