Excerpt from: Kurt & Barbara Aland, The Text of the NT, (Princeton, 1987) p.196
Barbara Aland offers a succinct and up-to-date summary of the current knowledge of the Coptic New Testament, in her introductory book.
Taken from: Kurt & Barbara Aland, The Text of the NT, (Princeton, 1987) p.196
4. THE COPTIC VERSION
The difficulties posed by the Coptic versions of the New Testament differ in kind from those of the Syriac versions, but they are no less challenging. The early period of Christianity in Egypt lies completely in obscurity.
All accounts of the beginning are legendary, eg., of Mark founding Christian churches, or the note in Codex Bezae Cantabrigiensis (D) that Apollos recieved his Christian training before leaving his home in Egypt. Even the Greek-speaking church does not appear there before A.D. 180/190, but then it occurs in a most impressive way, first with Bishop Dematrius of Alexandria, and then with the Alexandrian Catchetrical School under Clement, who was soon succeeded by Origen.
Evidence of the earlier presence of Christianity is provided by NT papyri. If P52 was written about 125, there must have been Christians in Egypt at that time. The lack of any reference to the church in Egypt before 180 is probably to be explained by the gnosticism of the churches there, which hindered their recognition by official churches elsewhere.
While we have no information about the beginnings of the Greek speaking church, we know even less about the beginnings of the Coptic church. At least as far as its official representations are concerned, the Egyptian church was Greek-speaking well into the 6th century and beyond. Nearly all the writings of its theologians and bishops were in Greek, and the survival of fragments of the Easter epistles of Athanasius (295-373) in Coptic presents a unique exception. It is significant for the close relationship between Coptic and Greek that the Coptic alphabet is itself largely an adaptation of the Greek alphabet, augmented with seven letters to accommodate its special needs.
And yet by the end of the 3rd century, or the beginning of the 4th century at the latest, there have existed a definite and rather extensive tradition of the NT text (together with at least the Psalms from the Old Testament, if not more). When Anthony withdrew into the desert (shortly before A.D. 300), he spent the day reciting substantial parts of the scriptures from memory. This must have been in Coptic, because Anthony was poor in Greek [at the Greek language]. And when Pachomius instituted his monastery about 320 A.D., the rules for the monks included a regular reading of the scriptures. This also assumes the availability of Coptic manuscripts, because few monks in the monastery were competent in Greek. But this is only one part of the problem.
Our grandfathers were distinguished only by three Coptic dialects: Sahidic, and Bohairic, and Fayyumic. Today Akhmimic, Subakhmimic, Middle Egyptian, and Protobohairic are also recognized. Precisely how these seven dialects of the various regions are mutually related and how the Coptic language developed are subjects for the greatest variety of speculation amoung specialists, with no solution in sight.
While this is true of the linguistic scene, it is equally true of the history of Coptic Bible translations.
Further, there are two extensive editions of the Coptic NT (of four and seven volumes respectively) edited by George Horner  in the principal dialects of Bohairic and Sahidic.