An example of the world's first postage stamp, the Penny Black, is being offered at a Sotheby’s auction in December. Dating from 1840, the item is "the earliest securely dated example of the first postage stamp," according to the auction house. “It took me three years with a team of people to collect the information and to be able to validate. It is certified by all of the top authorities,” said Alan Holyoake, current owner of the Penny Black stamp. Inside Edition Digital’s Stephanie Officer explains.