The Elder, to the elect lady and her children, whom I love in truth, and not only I, but also all those who have known the truth. (2 John 1:1)
At the time of the apostles, it was more appropriate to begin letters with who was making the address than to close them. John could have begun his address with several titles: "The disciple whom Jesus loved," "The apostle," "Son of thunder," "Brother of James" or many other titles of honor. Nonetheless, he chose to introduce himself as, "The Elder." The office of Elder is achieved by not only the passing years of experience, but by the attainment of understanding. It is not an elected office, but a recognized one. A man is not deemed an elder by popularity or political maneuvering. He is received as an elder by his relationship and obedience to Christ and his love for the church. All one has to do is study the life of John to see that these were the qualities of his person and characteristics of his office.