Happy birthday, Penny Black! The world’s first adhesive postage stamp was introduced 175 years ago today, on May 1st 1840, as part of Sir Rowland Hill's postal reforms which paved the way to the modern postal system.

Featuring the profile of Queen Victoria, the Penny Black was sold for just one year, as it was discovered the red ink being used to cancel it was too easily removed… In 1841, it was replaced by the Penny Red, which was easier to cancel using black ink.
It’s not a very rare stamp, as over 68 million specimens were printed, but very few complete sheets have survived. The ones that have now belong to the British Postal Museum and you can see them up close on their upcoming exhibition about this famous stamp. It will run from May 6th until August 7th, in London.