Samuel Clarke says,

“414. [Rev 1-DS] 8. I am Alpha and Omega, the Beginning and the End, saith the Lord, [in several MSS …the Lord God,] which is and which was and which is to come, the Almighty. [Gr. ὁ παντοκράτωρ, the Supreme Lord over all]…”

Παντοκράτωρ [Supreme over All] was ordinarily by Ancients (Saith the learned Bp. Pearson) taken for the Father: As Origen, book the 7th against Celsus;…the prophecies, in which (saith he) either…the Supreme God over all, or the Son of God, or the Holy Spirit was believed to be the speaker. And according to this general Confession did Polycarp begin his Prayer at his Martyrdom; …O Lord God Almighty, [or Supreme over  all;] the Father of thy beloved and blessed Son Jesus Christ.—And Constit. Apost. Lib. I. proem…Who have taken confidence to call the Supreme God, Father. Pearson on te Creed, pag. 41, Edit. 4th.

Again, pag. 42 By the First, [the Title…Almigty,] they seem to signify the Rule and Dominion which God hath over all.And again : From the Use of the sacred Writers, from the Notation of the Word in Greek. And from the testimony of the Ancient Fathers, we may well ascribe unto God the Father, in the Explication of this Article, [I believe in God the Father Almighty…] the dominion over All, and the rule and government of all.

Again, pag. 43. He——–is——– the only Potentate; because He alone hath all Power , of Himself; and whosoever else hath any, hath it from Him, ether by donation or permission. And again: He hath all Power over every thing, as being Absolute and Supreme.”

The Scripture Doctrine of the Trinity, pg. 62-64

First I would like to point out that the Alpha and Omega reading in Rev 1:11 is not found in the Westcott-Hort nor in the Majority Text. http://openscriptures.org/prototypes/manuscript-comparator/?passage=rev+1%3A11&view=parallel&strongs=1. It appears in the Textus Receptus which is well known for its textual additions.

Samuel Clark’s point is defended by an examination of Scripture. In Rev. 1, verse 2 we have a distinction between God and Jesus Christ; 1:4 distinguishes between he which was and is and is to come from Jesus Christ;1:6 refers to Jesus’ God as the Father; 1:12-13 distinguishes between the voice that cried alpha and omega from the son of man; Rev. 21distinguishes between the Lord God and the Lamb as does Rev. 22.

Now Rev. 1:17 is the strongest passage for the Triune Sabellianism. However, as Clarke pointed out Rev. 1:17 does not include the language of “the Almighty” [Παντοκράτωρ].

This word, Παντοκράτωρ shows up in 10 passages in the New Testament and none of them refer to the Son. They all refer to the Father. http://www.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=G3841&t=KJV