A museum in China is offering 10,000 yuan ($2,000 AUD approx.) to anyone who can decipher inscriptions written on six gold coins.
The coins were first discovered in a small glazed pot on a farm in the southern Hunan province in the 1960s. The coins were manufactured during China's Yuan dynasty, but they are believed to be written in a rare form of Arabic. Since arriving at Jinshi City's museum in the 1980s, archaeologists have remained puzzled.
They are not alone - hundreds of people have dedicated their lives to deciphering the meaning behind historic texts. Some have succeeded, but many puzzles still go unsolved. In a stroll through history, here we've collected five of the most influential and difficult challenges of cryptanalysis.
1. Rosetta Stone
The Rosetta Stone dates back to 196 BC, but in the modern day we rediscovered it in 1799 - inscribed in three different scripts, it provided an excellent puzzle for archaeologists. As the stone carried essentially the same text (a decree from Egyptian King Ptolemy V) in three languages, it provided the first key to Ancient Egyptian hieroglyphs, deciphered by Thomas Young and Jean-François Champollion.
2. Voynich manuscript
The 15th century Voynich manuscript has been described as the world’s most mysterious text. The 240-page long book is written in an unidentified writing system and contains images of plants and naked women. Throughout history many cryptographers have worked on figuring it out, and it has even been examined by a team of prominent World War Two code breakers - but to this day the meaning of these pages remains unknown.
3. Phaistos Disc
Hundreds have made attempts at deciphering the fired clay disc discovered on the Greek island of Crete. Despite Dr Gareth Owens of the Technological Educational Institute of Crete revealing that the disc inscribes a prayer to a mother, many in the archaeological community think that there is still not enough context available for specific meaning and use of the artefact. Some even think the item is a total fake.
4. The Shugborough Inscription
The Shugborough Inscription is a sequence of ten letters - O U O S V A V V, placed on a line between the letters D M - carved onto the 18th-century Shepherd's Monument. It has never been properly explained, and is another of the great puzzles that cryptographers are still scratching their heads over.
5. Mayan script
Called one of the most visually striking writing systems of the world, the Maya hieroglyphic writing is exceedingly complex, and it has been found all over monument carvings, painted pottery, and in their ancient texts. The decipherments of these glyphs has been a laborious process spanning decades, and while scholars agree that most of the texts are now readable with fairly high accuracy, new discoveries on to these texts are still coming to light.