U.S. postage stamps issued earlier than 1930 are more likely to sell for a premium higher than face value as they are rarer. More specifically, unused postage stamps minted in the 1800s are usually the most valuable.  Three of the most valuable stamps to sell at public auction are the 1868 Ben Franklin Z Grill ($3 million), 1918 Inverted Jenny ($1.74 million) and the 1867 Abraham Lincoln Z Grill ($1.6 million).