Long thought to be an Assyrian tablet, computer analysis has matched it with the sky above Mesopotamia in 3300 BCE and proves it to be of much more ancient Sumerian origin.
Unfortunately, considerable parts of the planisphere are missing, approximately 40%, damage which dates to the sacking of Nineveh.
The reverse of the tablet is not inscribed. Some call this the "Sodom and Gomorrah Tablet" because it describes a comet or asteroid which some think destroyed Sodom and Gomorrah about 3300 BCE.
For more information see Alan Bond and Mark Hempsell's book about this tablet called "A Sumerian Observation of the Kofels' Impact Event."