John’s Revelation is also found in complete Greek versions in the 4th century Codex Sinaiticus and in the late 4th/early 5th century Codex A (Alexandrinus), as well as in the 5th century Codex C (Ephraemi Rescriptus). Another complete Greek version of this work comes to us in uncial 046 dated to the 10th century, with other partial Greek editions of Revelation found in uncial 0169 (4th century), uncial 0163 (5th century), Codex Porphyrianus (9th century), uncial 051 (10th century), uncial 052 (10th century), and P. Oxy. 4500 (uncial 0308), a Greek fragment from the 4th century containing Revelation 11:15-16; 11:17-18.
In spite of this wealth of early and later textual support through to the 10th century, I am occasionally asked about the textual credibility for John’s Revelation in light of the textual support for other books of the New Testament, as if by comparison there may be less reason for believing we have a reliable copy of John’s Revelation than we do for other writings from around the time of the first century CE. At times I have even caught myself reflecting similarly about the textual support for John's Revelation, likely for several reasons.
John’s Revelation may at times be put into a different class or category from other New Testament books because it is not included in some important early New Testament texts. For example, the Old Syriac (Curetonian and Sinaiticus [late 2nd – 5th centuries]) does not include John's Revelation, nor does the Syriac Peshitta version (early 5th century). (But the 6th century Syriac Philoxenian/Harclean version does include Revelation.) Perhaps more important, John’s Revelation is not in one of our best New Testament witnesses, the 4th century Codex Vaticanus (B).
Each time I consider the reliability of the text of John's Revelation, though it is much different than either the Illiad or the writings of Josephus in terms of its content, two things stand out as well: 1) It is unclear whether John's Revelation was originally written or received in Greek; however, 2) the Greek text of Revelation we have today is based on a good amount of important early papyri and other credible, ancient texts, not to mention the many quotations of John's Revelation in the writings of numerous Christians from the second century CE forward which I have not here discussed.
The excellent textual and historical testimony for John’s Revelation is most evident when it is compared with other ancient Greek works, such as those by Homer or by Josephus, whose writings come to us from the same quarter century or so period as John’s Revelation (70 – 100 CE).
Indeed, if these writings with their comparatively limited textual history come to us with much content fit for use in defining and in reconstructing parts of our past, then perhaps the reliability of the text of John's Revelation will do the same, or prove beneficial in other ways as a reliable text and reference to early Christianity. If nothing else, we have good reasons to believe the text of John's Revelation is more reliable, textually, than other reasonably reliable, non-biblical, historical writings.
They then chose ten men by lot out of them, to slay all the rest; every one of whom laid himself down by his wife and children on the ground, and threw his arms about them, and they offered their necks to the stroke of those who by lot executed that melancholy office [Whiston, The Works of Josephus (Hendrickson, 1987), Book 7, Chapter 9.1].
 The earliest explicit references to John's Revelation appear to be in Chapter 34 of Clement's First Letter (late first century CE) and in Chapter 3 of the longer version of Ignatius' Letter to the Smyrnaens (early second century ?), in the Fragments of Papias (60 - 140 CE), and in Chapter 81 of Justin Martyr's (105 - 165 CE) Dialogue with Trypho. See also G. Mussies, The Morphology of Koine Greek as Used in the Apocalypse of St. John: A Study in Bilingualism (SNT 37; Leiden, Brill: 1971), pages 37-38.