The most valuable rare stamp in the world is the British Guiana 1c Magenta.
The stamp was auctioned in 2014 and sold for $9.48 million, though that price tag dipped considerably when it was auctioned again for a price of roughly $8.3 million in 2021.
According to Invaluable. com, the stamp was included in an 1856 emergency run that was produced after the initial shipment of ...