The book of Revelation is a book about the triumph of the people of God over the empire, that is, the triumph of the kingdom of Jesus’ people over the Roman empire with its emperor worship.  Everyone had a mark; you were marked by emperor worship or you were marked by Jesus’ worship (Revelation 7:3; 9:4; 13:6, 16-18; 14: 1, 9; 17:5; 20:4). If you worshiped the emperor you were marked for him and if you worshiped Jesus you were marked for Him.  It is said of the Jesus-government people, the ones who had overcome, that they had the mark of their true king on their forehead.  “They will see his face, and his name will be on their foreheads” (Revelation 22:1-5 ESV).  Throughout their lives they had clung to Him as their only Lord; they had believed that if Jesus was Lord then Caesar was not Lord.  Now they have His mark on their heads at the end of their lives, because that is the way they had lived their lives, the way they had been governed.  In the end they are the very ones who see His face.