The British Guiana 1c Magenta was bought by rare stamp dealer Stanley Gibbons ... them to be taken out of circulation - but one of the one cent stamps survived. It was discovered around 20 years ...

One sold for £400,000 in 2010 ($535,000 today). William H. Gross was a famous stamp collector, and this 2 cents Hawaiian Missionary stamp was the most valuable stamp in his collection.