This record of the sayings of Jesus has excited scholars and ordinary readers alike since the discovery of the Coptic text (c.350CE) at Nag Hammadi in the mid-twentieth century.
The Coptic text is the only complete copy to have survived. It is a translation into Coptic from the earlier Greek text (pre 200CE) which has only survived in fragments from three separate copies, two dated to 200CE, and one to 250CE. All four copies have been found in Egypt.
Some scholars have hypothesised that the core of the text may have originated in Aramaic but we have at present no way of evaluating this. It is however probable that Aramaic was the language in which these sayings would have been delivered to their original audience.
If we take the view that this text was assembled by Thomas himself, then we can assume a date in the 40-65CE range.