In Marvin Meyers nwer book, "The Gnostic Discoveries" he says:
The Gospel of Thomas is the 2nd tractate of Nag Hammadi Codex ll, and is situated immediately after the SEcret Book of John and just before the Gospel of Philip.
The variations among the several texts makes it clear that the Gospel of Thomas went through several editions, and changes could be made from one edition to another.
Such fluidity in the written word was characeristic of the textual world of scribal acitivity prior to Guttenberg and the invention of the printing press.
The Gospel of Thomas was translated from the Coptic no later then the middle of the 4th century or more likely some time before then, but the Greek paprus fragments hae been dated much earlier at the beginning of the 3rd century or later.
On this basis of such suggested dates, Grenfell and Hunt the first editors of the Oxrhynchus papyri, estimated that the original documents must have been composed at least half a century earlier around 140 at the latest.
More recently, Soren Giversen has revised these dates and has stated that on papyrological grounds,
the Gospel of Thomas may be assigned earlier dates so that the date of it's composition may be pushed back even further, perhaps into the 1st Century.
The textual evidence for an early date thus may rival for the Gospel of Thomas, that of any of the New Testament gospels.
Further, the Gospel of Thomas illustrates contents that are usually judged to belong to the first century; disagreements about apostleship, uncertainty about the role of James the righteous (brother of Jesus);
interest in Jesus sayings and so forth.
Sayings in the Gospel of Thomas also seem to be transmitted in a form that is earlier then the form we have in the canonical gospels.
Such may be noted for instance in parables. Thomas preserves parables of Jesus simply as stories, BUT the New Testament gospels append allegorical interpretations to the parables and apply them to new situations.
One saying in the Gospel of Thomas (17) offers words of Jesus
"I shall give you what no eye has seen, what no ear has heard, what no hand has touched , what has not arisen in the human heart" -- and that sounds very much like Paul cites in his description of wisdom to Christians in Corinth (1Cor2:9) in the middle of the 1st Century.
IF the composition of the Gospel of Thomas may be given a date in the early 1st century, then Thomas may take us back to a place that is much closer to the historical Jesus, and the Gospel of Thomas together with the sayings gospel Q may provide strong evidence for Jesus as a teacher of wisdom.
(from page 64 - The Gnostic Discoveries" by Marvin Meyer.
"The Impact of the Nag Hammadi Library"