Credentials of the Church
Whether its a policeman's badge, a college degree or a serviceman's orders, everyone expects and understands the importance of credentials to verify that 'you are who you say you are'. We should expect this from the True Church, also.
In the Old Testament Book of Numbers , geneological lists of 'begats' are used to establish the validity of the tribes of Israel and their descendants. In the New Testament, and the New Testament books of Matthew and Luke
use this to establish that Jesus can vailidly claim to be a descendant of the Tribe of Judah from which the promised Messiah would come.
The Church used prayer and the laying on of hands to establish the legitimate successors of the first Apostles (Acts 13:2-3 for St. Paul and St. Barnabas) and for other offices (i.e. deacons in Acts 6:6). This continues until today. The unbroken line of
men who were ordained by prayer and the laying on of hands from recognized, legitimate authority of the Church can claim Apostolic Succession...direct spiritual descendents of Christ and the Twelve.
Since only men who understood and upheld sound doctrine were ordained, the credentials of the True Church are established clearly in our Third Millenium.
The Orthodox Church has these proven credentials.
Additional Reference