Peter A. Lillback suggested in his book, "Binding of God, The: Calvin's Role in the Development of Covenant Theology", that John Calvin had Proto-Covenant Theology ideas, because Covenant Theology was developed after Calvin by his followers. Calvin's teaching on Covenant Theology, especially in the Institutes of the Christian Religion, Book II, were more explanation of the use of the terms for "covenant" used in the bible: i.e., "covenant" is the Greek work, diatheke, and the Hebrew word, bereth, and the Latin word, testamentum. Calvin was a master exegete and his Proto-Covenant Theology was a ground breaking exegesis of these words, rather than a complete system that explaned everything in the way that the later Federal Theologians were to do. Calvin also explored other aspects of Covenant Theology, such as the two adams being covenant heads because that idea is clearly stated by Paul, however, putting the Two Adams together with all there terms was not present in Calvin as in the clear system of Federal (ie Covenant) Theology conceived in detailed form by Johannes Coccejus. Nor was the simplest forms of the Covenant of Works vs Covenant of Grace as is in the Westminster Confession completed in Calvin either. Nor were the relationship between the multiple covenants in Scriptures explained by his genius either, such as Adam, Noah, Abraham, Mosaic, Davidic, and the New Covenant. 

Sometimes in some Reformed Churches today, the continuum between the Old Covenant and the New Covenant is explained in terms of abrogation by say that the Mosaic consists in three parts: Moral, Judicial and Ceremonial where Jesus's Passsion had abrograted the Judicial and Ceremonial aspects but the Moral aspects remains which are primarily defined as the 10 commandments. However, there are problems with this explanation because, for instance, the Sabbath has moral, judicial and ceremonial aspects that cannot be divided up easily. The 613 Mosaic Laws likewise cannot easily be divided up in to this trichotomy either. It is similar to trying to find Q in the Synoptics Gospel, with all those problems. This strategy is useful for preaching Law, so the difficulties are usually ignored. Occasionally, I've had friends say that the Old Covenant is in full force in entirety, and try to work through all those problems contain. It's a hard problem, but the greatest error to make is to see the Old and New Covenants as two separate covenants, which is best represented by the aberrant Dispensational Theology and all its nonsense (and I'll leave the proof of this statement as an exercise for the reader.)

The later Federal Theologians developed a third covenant, The Pact of Redemption or Covenant of Redemption, which is like an intratrinitarian Covenant that God the Father made with God the Son, to send the Son as redeemer of fallen man. This truth demonstrates how deep the rabbit hole goes. It is not as if God was surprised by the Fall of Man, or as if he did not foresee it from the beginning, such ideas are absurd and laughable. As Karl Barth said, we have no other knowledge of God other than as "God with us" and as we look at God the Son before the incarnation, we only see God the Son as the God who will be with us in the incarntion so that we cannot conceive of God in any other way. To imagine Jesus Christ other than his incarnate form that was coming into the world (ie logos asarkos) is to say things about God in his wholly other and unrevealed form, and of which we have no knowledge to speak about God in this way. I mentioned Karl Barth, because in his Church Dogmatics, Vol IV.1, The Doctrine of Reconciliation, Section 57, there's a short history of dogma about Covenant Theology that discusses the origins of Proto-Covenant Theology in Calvin and the early reformers, and contrasts them with the developed forms of Johannes Coccejus and the Westminster Divines that praises Calvin's early work, and offers course corrections to a beautiful set of dogmas. 

"What is done way (Calvin) is only its "economy," the form in which it is revealed and active in the events of the Old Testament this side of the last days. In accordance with the completely changed conditions of the last time this form will certainly be altered, and so radically that it will no longer be recognizable in that form, and to that extent a new covenant will actually have been concluded: The form in which it was revealed and active in all the events from the exodus from Egypt to the destruction of Israel and Judah was such that in it the faithfulness of the power of Yahweh seemed always to be matched and limited by the perpetually virulent and active disobedience and apostasy of the covenanted people. The prophecy says that this will end in the last days. "

- Karl Barth, Church Dogmatics, Vol IV.1, page 33.

Karl Barth agrees with John Calvin's explanation of the relationship between the two covenants in this way: Calvin said that the Old and New Covenant are basically one covenant but under different economies. It is similar to a Will and Testament for a child heir whom is not yet an adult; there are stipulations on the access the child has to his inheretence until he comes to fullness of age. So the circumstances of the Old Covenant leading up to Jesus were like a Tutor or a Will that were intended to go away from the very beginning at once Jesus appeared incarnate and accomplished reconciliation, and it was to prepare us for Jesus and its economies were never intended to remain forever. So this is why, according to Calvin, that it is wrong to turn away from Christ and look back to the old economy of the Old Testament, because it mocks the true substance in the abrogated form. It's prefering love letters from a loved one, in the presense of the loved one once reunited to them. "I'd rather read your love letters than actually see you" are mocking and wicked words.

Karl Barth concludes that the highest form of Covenant Theology (or Federal Theology) was that of the Dutch Reformed theologian, Johannes Coccejus (1603 – 1669). Coccejus saw the continuity of the two covenants in a different way than the traditional Old Covenant verse New Covenant dichotomy. He prefered to explain Federal Theology in terms of the old form of the covenant and its revealed form, and that the are five progressive abrogations from the first firm to the true form of the one Covenant.  The substance of the first form of the Covenant in Adam was such that the violation of the one Covenant's first economy was necessary for us to ultimately get to the underlying final economy of the one Covenant of Grace.

The following quotations are from Karl Barth's explanation of the five abrogations of Johannes Coccejus' Federal Theology:

1. "The first abrogation is by sin."
2. "The second is related to the first and consists in the institution of the covenant of grace."
3. "In the third abrogation of the covenant of works as Coccejus sees it, we return to the earth and history. It is the announcing of the covenant of grace in the economy of the Old Testament prefigured in the proto-Gospel of Gen. 3:15f."
4. "The fourth abrogation of the covenant of works Coccejus calls the death of the body, i.e., the sanctification which in the work of Christ goes hand in hand with justification, sanctification as purification, as the destruction of the works of the devil and the darkness of the intellect and the badness of the human will. The Law is now a weapon in the warfare of the spirit against the flesh."
5. "The fifth and final abrogation of the covenant of works is what Coccejus calls the reawakening of the body. He is thinking here of the eschatological redemption and consumation. WIth this the validity of the covenant of works ceases altogether--that is, for the righteous."

--Karl Barth, Church Dogmatics Vol IV.1, pg 59-60. http://books.google.com/books?id=X-wOMgH0ar0C&lpg=PA57&ots=WzUH1Qljpf&pg=PA56#v=onepage&q&f=false

Barth noted that the Old Covenant vs New Covenant was made in terms of distinctions of preservation vs grace since the Adamic and Noahic Covenants were universal. Barth thought that the later reformers emphasized a distinction between the benefits of preservation vs grace/mercy to the point of going away from one covenant to two covenant system due to double predestination being the reformer's answer to the two fold nature. So that only the preservation part of the covenant remained universal, and the true form of the covenant was not universal but only for the elect.  So this is a similar discussion to how the church could contain reprobate members, such as the apostle Judas who was an elect demon and a devil from the beginning (as Scriptures say). So Barth believed that Calvin and the early reformers affirmed the universalist nature of the one covenant and thought it was wrong that apart from Coccejus, it was turned into a two fold covenant of Nature or covenant of Works in contrast to a covenant of Grace. I think that this is a reasonable critique, and then Barth went on to say that the basis of the covenant is not the intertrinitarian pact of redemption, as the later Federal Theologians believed, but it is actually as its basis in the incarnation "god with us" and the incarnation is the basis of the one covenant and is the basis of all creation. Hence the priority of the incarnation as the basis for the covenant's power then there's a bunch of stuff about the reciprocity with in the covenant between God and man. I believe Calvin, Coccejus and Barth's explanation of the abrogations of economies are a part of the one Covenant of Grace, but contra Barth, that it is an eternal unilateral covenant which Barth criticized. Barth sees the covenant in relationship and in reciprocity between God and man, but this is beyond the this blog's content.