These are the most valuable stamps from around the world ... The Benjamin Franklin Z Grill is a 1-cent stamp from 1868 created with a briefly used grill that left tiny Z-shaped indentations.

Another holy grail for collectors, the U.S.-issued “Z Grill” is one of the rarest and most valuable stamps ... In 1995, a 2-cent Blue Hawaiian Missionary stamp sold for $440,000 at auction.