China’s first postage stamps from the Qing Dynasty ... the U.S.-issued “Z Grill” is one of the rarest and most valuable stamps in American philately thanks to its unique “grill” design.

The 1851 12d Black Empress is far from the rarest Canadian stamp ... been used as postage for a love letter between two cousins). It sold for $1 million in 1981 and increased in value since ...