Irenaeus of Lyons, writing in the second century, said in his book, Against Heresies (Book 5, ch. 30), that he thought one of the most likely interpretations of 666 was ΛΑΤΕΙΝΟΣ, or Lateinos, for the Latins were presently ruling and were the fourth and last kingdom foreseen by Daniel. But he went on to say that no one could be sure until the kingdom was divided into ten. So he expected the Roman empire, then reigning, to be divided into ten, and soon thereafter would the antichrist be revealed.
That’s a tidbit picked up by reading L. E. Froom, The Prophetic Faith of Our Fathers–a great work which shows that Seventh-day Adventists did not create their prophetic interpretations from scratch. Froom notes that Hippolytus liked Irenaeus’ solution, and was agreed that Scripture pointed to the Latins. Hippolytus identified the Babylonian harlot as Rome, as did Victorinus, Jerome, Tichonius (a Donatist, saw it specifically as the Roman church and bishops), and Augustine (thought he would sit in the church); Spiritual Franciscans began applying it to the papacy, including Joachim of Fiore and Pierre Jean d’Olivi; so did the Waldenses.