Real World Background
The Rosetta Stone was carved in the year 196 B.C., and bore a state decree issued by the then-ruler of Egypt, Ptolemy V, in three writing systems: Egyptian hieroglyphics, Demotic (a sort of everyday writing in Hellenistic Egypt), and the Greek alphabet. It was re-discovered by Napoleon's soldiers, campaigning in Egypt in 1799, while digging a trench. The British captured it from the French in 1801, and took it back to London, where it eventually became part of the British Museum's collection. The French scholar Jean-Francois Champollion was able to use the Greek version of the decree (which shared the same text with the other two inscriptions) to translate the Egyptian hieroglyphics (whose meaning had been lost since the end of ancient Egypt and the priests who had used hieroglyphics).
The Rosetta Stone remains in the British Museum to this day, and was even included in A History of the World in 100 Objects by Neil MacGregor (an examination of world history through a hundred exhibits in the Museum) as No. 33.