The Copts have an interesting tradition with respect to the Sign of the Cross.
First of all, they place the right hand on the head for "In the Name of the Father" and their understanding is that when we do that, we do not see our hand or fingers (because it is on the head) symbolizing the fact that the Father is above all as God Almighty.
Then we bring our hand down to our stomach to signify the Incarnation of the Son Whom we do see because He came down to earth and was made Man in the Womb of His Most Holy Mother.
Then we move our hand to our LEFT shoulder over our heart which is where the Holy Spirit of God makes His abode with us.
Another explanation given in the Coptic tradition - also used to vehemently denounce the Greek way of moving to the right shoulder first - is that Christ the Divine Saviour has brought us out of sinfulness (left shoulder) into His Divine Light (right shoulder).
But when our hand is on our left shoulder, we say "And the Holy Spirit" and then move to the right shoulder where we end with "One God, Amen"
In the Armenian tradition, the Sign of the Cross is the same as in the Coptic tradition, except that after the words "One God" we move our hand onto the middle of our chest and bow our heads slightly as we say "Amen"
The Copts will use three fingers when making the Sign of the Cross but also when Roman and Byzantine commentators have historically and mistakenly assumed was the use of one finger.
In fact, it is the Christogram with the index finger out with the middle finger bent down like the Old Believer form.
The use of the fingers has its own history . . .
Christians would use one finger to Cross themselves with initially and that on the forehead, lips, heart and over other people and objects to be blessed.
The RC Little Sign at the reading of the Gospels continues that ancient tradition to this day.
The Church of Antioch and its emphasis on the Two Natures of Christ led to the use of two fingers extended in making the Sign of the Cross.
Following Blessed Theodoret of Cyrrhus (a full saint in the Assyrian Church of the East), the index finger, representing the Humanity of Christ is joined to the middle fingers slightly bent to represent the Divine Son of God coming down to earth, with the thumb and other two fingers joined to signify the Trinity. St Peter the Damascene said "By two fingers we confess Christ in Two Natures and with the one hand we confess He is One Christ."
So the old Antiochene Sign of the Cross continues among Old Believers and among Armenians in the eastern part of their country. One can find it among the Miaphysites and I have seen it used by the Ethiopians I have had the blessing to meet here.
I use the old Antiochene method when crossing myself when saying the Jesus Prayer with bows.
My may surmise that the ancient methods of holding the fingers for the Sign of the Cross were directly related to the Person of OLGS Jesus Christ in the first instance (as the old Believers say "only the Son of God was crucified and not the whole Trinity").
Thus, the later RC tradition of holding five fingers for the Sign of the Cross related to the Five Wounds of Christ, while a later tradition, does reconnect the Sign of the Cross back to its earliest roots in this respect.
