Clay tablets were used for accounting, literary, administrative documents. [Indian historical tradition attests to the use of copper plates for conveyancing property rights. It is notable that some inscriptions are inscribed on copper tablets. So far, no other civilization has recorded such use of copper plates as recording devices for economic transactions.]
The clay tokens were some of the early findings of mesopotamia but it seems as if the Mesopotamian's gave up the use of such clay tokens all together after a particular length of time.
Cuneiform documents were written on clay tablets, by means of a blunt reed for a stylus. The impressions left by the stylus were wedge shaped, thus giving rise to the name cuneiform ("wedge shaped," from the Latin cuneus, meaning "wedge").
The Sumerian script was adapted for the writing of the Akkadian, Eblaite, Elamite, Hittite, Luwian, Hattic, Hurrian, and Urartian languages, and it inspired the Ugaritic and Old Persian national alphabets.
Sumerian Clay Tablets
In the late fourth and third milleniums B.C. a people called the Sumerians began to develop a writing system called "cuneiform" ("wedge-shaped"), written on wet clay with a sharpened stick, or stylus. At first the Sumerians used a series of pictures ("pictograms") to record information having to do with business and administration, but went on to develop a system of symbols that stood for ideas and later sounds (usually syllables).
In the later stages of Sumerian writing there were about 600 signs that were used on a regular basis. Newer symbols were closer to nature than ever. They represented it in the true form. Also another unique feature of the new system involved not using similar representations of similar objects.
The earliest record of written work-clay tablets- which date back to around 3200B.C. were discovered by archaeologists form the Oriental Institute at Tell Asmara in modern day Iraq.With clay being a difficult material to draw lines and curves on, the writing on these early tablets consist of mainly simple drawings, pictures or pictograms which usually symbolise an object or idea.
If it was comparatively easy to symbolize agricultural products with a drawing or simple symbol, it was more difficult to write the name of a person. To solve this problem, somebody thought of using short words, mono or bi-syllabic, and to unite them in the same way we are doing today with the rebus. Around 3000 BC, other signs were introduced which were not used to mean an object, but rather a name for the object (phonograms).