Are you a philatelist, or do you just have a passing interest in these glue-backed pieces of paper?

The first credible claim for the development of a real postal system comes from around 550 BCE in Ancient Persia, but the first adhesive stamp was issued in 1840 when the United Kingdom issued the "Penny Black" which cost one penny. These days a mint (perfect condition) Penny Black would cost you about $4,000 at auction!