I'll try to answer but I am watching UFC, priorities...you know.
The Adamic, Noahetic, and Abramic (circumcision) covenants chronologically came before the Mosaic (law) covenant. Under which primary covenant do we lump them?
Adamic, covenant of works, 'do and live' in the garden.
Noahic, a republication of the everlasting covenant of grace toward God's elect:
"In order to attain a right understanding of the various covenants which God made with different men, it is highly essential that we carefully distinguish between the literal and the figurative, or the outward form and its inner meaning. Only thus shall we be able to separate between what was merely local and evanescent, and that which was more comprehensive and enduring. There was connected with each covenant that which was literal or material, and also that which was mystical or spiritual; and unless this be duly noted, confusion is bound to ensue. Yea, it is at this very point that many have erredparticularly so with the Abrahamic and Sinaitic covenants."
"Each covenant that God made with men shadowed forth some element of the everlasting covenant which He entered into with Christ before the foundation of the world on behalf of His elect. The covenants which God made with Noah, Abraham, and David as truly exhibited different aspects of the compact of grace as did the several vessels in the tabernacle typify certain characteristics of the person and work of Christ. Yet, just as those vessels also had an immediate and local use, so the covenants respected what was earthly and carnal, as well as what was spiritual and heavenly. This dual fact receives illustration and exemplification in the covenant which is now before us. That which was literal and external in it is so obvious and well known that it needs no enlarging upon by us here. The sign and seal of the covenantthe rainbowand the promise connected therewith were tangible and visible things, which the senses of men have verified for themselves from then till now. But is that all there was to the Noahic covenant?"
"Thus the Noahic covenant served to bring out in a new light, and establish on a firmer basis, the unfailing faithfulness of Jehovah and the immutability of His purpose. An assurance to that effect was specially needed just after the Flood, for it was over that basic truth that the judgment of the Deluge had seemed to cast a shadow. But the promises made to Noah, solemnly given in covenant form and sealed by the token of the rainbow, effectually reestablished confidence and stands out stillafter all these many centuriesas one of the grand events in Gods dealings with men; assuring us that, however the sins of the world may provoke the justice of God, the purpose of His grace unto His chosen people stands unalterably sure."
Correct me if I am wrong, but don't Presbyterians recognize three primary covenants? The covenant of redemption, grace, works. I think there is an important distinction, the parties involved. In the covenant of redemption, God the Father made an agreement with God the Son. While in the covenants of grace and works, God made an agreement between Him and men, one being unconditional (grace), the other conditional (works).
I guess I collapse the idea of the covenant of redemption with the everlasting covenant of grace. The everlasting covenant was made before time and revealed in time as the covenant of grace. So, I'm not opposed to the idea of separating the
pactum salutis I tend to view them as one in the same.
Pink, "The everlasting covenant or covenant of grace is that mutual agree[bless and do not curse]ment into which the Father entered with His Son before the founda[bless and do not curse]tion of the world respecting the salvation of His elect, Christ being appointed the mediator, He willingly consenting to be their head and representative. That there is a divine covenant to which Christ stands related, and that the great work which He performed here on earth was the discharge of His covenant office, is very plain from many Scriptures, first of all, from the covenant titles which He bears. In Isaiah 42:6 we hear the Father saying to the Son: I the Lord have called thee in righteousness, and will hold throe hand, and will keep thee, and give thee for a covenant of the people, for a light of the Gentiles. As a covenantee in it, Christ is thus given unto His people, as the pledge of all its blessings (cf. Rom. 8:32). He is the representative of His people in it. He is, in His n person and work, the sum and substance of it. He has fulfilled all its terms, and now dispenses its rewards."
Where are Presbyterians mixing grace with works? Infant baptism? Nah.
I'm saying the idea of a
one to one equivalent between circumcision and baptism cannot be found in scripture. This idea is not found before the Reformation. Infant baptism before the Reformation was performed to counter act original sin this is why the area that practice infant baptism in the early church also believed it did something (like baptismal regeneration) for the infant. It wasn't a covenant sign or seal to the early church but a rite to battle original sin.
Something interesting I learned recently about the physical line and seeds of Abraham...he was a gentile. Surprised me.
He was, like us...until we were called. Now we are in Christ, heirs to the promises and therefore spiritual Israel.

Thanks for the link, that reminds me, recently Ligonier Ministries put up audio (iTunes Podcast) of a friendly debate between John MacArthur and R.C. Sproul on Baptism.
Just remember brother, the third session where they have a back and forth isn't found on Ligonier.

I had it and might still have it if you want me to send it to you. MacArthur gets Sproul back peddling and he can't recover. I listened to the debate several times over the years.
Some cool charts and videos here:
1689 Federalism | The distinctive biblical theology of confessional particular baptists
Divine Covenants by Pink:
Divine Covenants by A.W. Pink-Contents
1689 LBC: Chapter 7: "Of God's Covenant"
Yours in the Lord,
jm
PS: Vera shouldn't be fighting heavyweight, that's crazy! He should stay at 205 or expect receive more beat downs.