Inverted Head 4 Annas

India's 1854 four annas was the first two-color stamp of the British Empire, so it had to go through the press twice: red frames first, then the blue heads of Queen Victoria the following day, once the sheets had dried. The rush to get the stamps on sale let errors slip through, and a few sheets received their heads upside down inside the frame. Nobody recognized the mistake until 1890, and 28 examples are now known. For collectors of British India it is the great rarity, and the clearest lesson on this list in how an error is born from the printing process itself.