This particular 1840 Penny Black is the world’s first postage stamp. It is expected to fetch up to $8.25 million at Sotheby's in December.
World's first postage stamp the Penny Black expected to sell for millions at auction - ABC News
World/United States and Foreign Postage Stamp Album 1940 unused hardcoverINV2880
The World's First Postage Stamp Could Reach $8.25 Million at Auction – Robb Report
World's first postage stamp goes to auction
Final push for Pluto's postage stamp
World's first postage stamp goes to auction
World's first postage stamp goes to auction
The World's First Postage Stamp Could Reach $8.25 Million at Auction – Robb Report
World's first postage stamp goes to auction
The World's First Postage Stamp is Worth Millions