I’m going to try to not get too detailed about the sources of the book of Revelation and keep it rather general, but some specific examples will be necessary.
It seems clear that the author of Revelation used several earlier sources, and that these sources were Jewish apocalyptic documents that dated to the time of the Great Revot of 66-70 AD, or immediately before it.
Notice that in spite of a Christian preface and ending, and several Christian sections, most of Revelation is of a very Jewish character. Instead of a Trinity, there are the “seven spirits of God” – an idea from Philo. It is God who sits on the throne and judges, not Jesus. It is not the 12 apostles who sit on thrones, as Jesus had promised, but 24 Elders. There is no sign of baptism or communion– rather faithful Israelites are “sealed” by an angel. The ark of the covenant features prominently, as does incense, lamps, a horned altar, and multiple offerings. Temple worship is clearly the pattern. The dead are judged by their works, out of the book of life (as mentioned in Exodus 32). Grace is mentioned only in the Christian prologue and epilogue.
Many of the places where Jesus or a Jesus figure is mentioned, it seems tacked on as an afterthought. Such as: “And cried with a loud voice, saying, Salvation to our God which sitteth upon the throne, and unto the Lamb.” (Revelation 7:10 KJV) This pattern is repeated over and over. In many of these sections, you could easily remove all the references to “the lamb” and the passage will still make perfect sense.
Unlike Christian martyrs such as Stephen, who pray for forgiveness for their persecutors, the martyrs in Revelation are out for blood:
When he opened the fifth seal, I saw underneath the altar the souls of those who had been killed for the Word of God, and for the testimony of the Lamb which they had [yet another apparent insertion]. They cried with a loud voice, saying, How long, Master, the holy and true, until you judge and avenge our blood on those who dwell on the earth? (Revelation 6:9-10 WEB)
The Messiah figure in Revelation is in stark contrast to Jesus. Unlike Jesus, who is born on earth and reigns in heaven, the Revelation Messiah is born in heaven to rule on earth. He descends in a robe drenched in the blood of his enemies with a sword coming out of his mouth ready to destroy all who oppose him.
Also, while the Christian prologue and letters point to a later date under Domitian, as I mentioned previously – several clues in the Jewish section point to an earlier period. Most famous is the “mark of the Beast”. As many are aware, “666” has long been known to correspond to the Greek title of Caesar Nero. The most recent research, however, indicates that the earliest reading was not 666, but 616, which would have corresponded to the Greek name of Caligula
This is a perfect fit, as Caligula, half-crazed, declared himself a God, and ordered a statue set up of himself in every temple in the empire. Only the Jews refused. Caligula was infuriated, and roared at a visiting delegation of Jews, "So you are the enemies of the gods, the only people who refuse to recognize my divinity." It was only Caligula’s sudden death that saved Jerusalem at that time.
“He opened his mouth for blasphemy against God, to blaspheme his name, and his dwelling, those who dwell in heaven… All who dwell on the earth will worship him, everyone whose name has not been written from the foundation of the world in the book of life of the Lamb who has been killed [another insertion]…It was given to him to give breath to it, to the image of the beast, that the image of the beast should both speak, and cause as many as wouldn’t worship the image of the beast to be killed. “
(Revelation 13:6, 8, 15 WEB)
But when the Jewish revolt began a few years later under Nero, the change of the number to 666 (representing Nero) would have made sense.
Other portions of the text point to authorship in 69 AD, just before the destruction of Jerusalem. For example:
They are seven kings. Five have fallen, the one is, the other has not yet come. When he comes, he must continue a little while. (Revelation 17:10 WEB)
Five Caesars fall (Julius, Agustus, Tiberius, Caligula, Claudius) One is (Nero) another comes for a brief time (Galba – who reigned less than a year). Then, a return of the beast is expected. In fact, if we ignore the reigns Otho and Vitellius, who lasted less than six months each, the very next emperor was Vespatian, who had personally supervised the destruction of Jerusalem.
“It was given to him to make war with the saints, and to overcome them. Authority over every tribe, people, language, and nation was given to him. “ (Revelation 13:7 WEB)
With the expansion of Claudius into Britan and the annexing of more provinces from the East, the Roman Empire at this point had expanded nearly to the boundries of the known world.
But since these appear to be several revisions of several Jewish documents (judging by the literary style) from slightly different periods, several different emperors are pointed to, and the final author “John” apparently didn’t bother to resolve all the contradictions.