There has been speculation that the reign of the Antichrist has begun, and that his servants are already being sealed with his seal and with the number “666”. I still don't see any agreement about what the seal of the beast really is, nor about the meaning of his number. My particular Church didn't give an authoritative interpretation of the thirteenth to twentieth chapters of Revelation and their symbols – the first beast, the second beast, the horns and heads of the beast, his seal and image and number, the whore of Babylon, etc.
I think the Antichrist in his last, personal incarnation, has not yet appeared. I don't think we know have all the prophecies relating to the times preceding the appearance of the Antichrist already been fulfilled? There will always be different understandings of the basic prophecies. " The third period" is in fact the time of the enthronement of the Antichrist, but does anyone know when exactly that will happen? Not yet.