The first question is about the supposed "replacement-pages" at this very spot. We get the first clue about them from F.H.A. Scrivener's popularization of Tischendorf's work, in his Collation of Sinaiticus (1867):
"In the deliberate judgment of Tischendorf, who has of course the best right to be heard on such a point, no less than four different hands were employed on the Codex Sinaiticus. He believes that:
The scribe A wrote the fragment of Chronicles, 1 Maccabees, the last 4 1/2 leaves of 4 Maccabees, Barnabas, and the whole NT excepting about six leaves.
To scribe В he ascribes the Prophetical Books and Hermas' Shepherd:
To scribe С the Poetical Books of the Old Testament, written in στιχοι or verses clause by clause, according to the sense, with two columns per page, just as in the great Codex Vaticanus, which in all other parts has three columns, but in the Poetical Books only two.
To scribe D he gives Tobit, Judith, the first 3 1/2 leaves of 4 Maccabees, and in the NT:
leaf 10 (Matt. 16:9—18:12),
leaf 15 (Matt. 24:36—26:6),
leaf 28, 29 (Mark 14:64—Luke 1:56), [Quire 77 folio 4,5]
leaf 88 (1 Thess. 2:14—5:28),
leaf 91 (Heb.4:16—8:1),
and possibly the first 32 lines of Rev. (1:1-5 up to ιυ χυ, fol. 126*), the last mainly upon grounds expressly assigned, which we shall speak of hereafter.
He further states that A and В much resemble each other, as also do С and D. On the other hand Tregelles, who by Tischendorf's permission examined the MS for three whole days in 1862, has observed no such diversity in the writing as would necessarily lead us to refer the several portions to different scribes;
Those who have not inspected the manuscript for themselves are scarcely entitled to express an opinion on a matter like this. We may venture, however, to say, that the published Facsimile plates (for the moveable type of the larger edition can hardly be relied upon in a question so delicate) show no such diversity as would have suggested to us Tischendorf's conclusions.Yet we know that Woide has suspected the same change of hands in the portion of the Codex Alexandrinus which he edited, and others too, with still greater show of probability, in the case of Codex Augiensis; though there is little doubt that each of these is the work of but one penman, whose hand would naturally vary a little with the quality of his materials, and as he became familiar with or weary of his task.
Notice, however, the peculiar shape of omega, with its tall central stroke, represented in our Facsimile (7). This form occurs in none of Tischendorf's plates, by him assigned to С or D, or in those portions of the NT in moveable type which are imputed to D, but eight times in the two he ascribes to В (II. XVII.), six times in one of A's (V), only once in A's other nine, always towards the end of lines, mostly reduced in size, and except on Plate V. mixed up with the more familiar ω *
We must add too, that the few leaves of the NT ascribed by Tischendorf to D are much freer from itacisms, or instances of false spelling, than those on either side of them: the transition is quite remarkable from leaf 9 of A to leaf 10 (Matt. 16:9 - 18:12) of D, and then back again to leaf 11 of A, as the reader may see for himself by consulting our collation.
These remarks, so far as they extend, would seem to suggest two scribes, A being identical with B, and possibly С = D ; the members of which pairs Tischendorf declares to be much alike; but whether the actual penmen be one, or two, or four, is of the less importance, as (in the N. T. certainly, and most probably in the Old) the whole work was clearly executed at the same time, and transcribed from the same older copy. " (- F.H.A. Scrivener, Sinaiticus )From the above, it seems plausible that scribe D at least is a different hand than scribe A, and that scribe D is a much better speller, something that should be detectable in the subsequent examination of other pages, to shortly follow.