Bpbasilphx, I think you have some confusion on these points.
Actually both Codex Vaticanus (B, 4th century) and Codex Alexandrus (A) are complete Orthodox manuscripts (although, as I show below, they are not necessarily the best manuscripts we have). The problem is that the translators have not always translators have not always translated
I am surprised you mentioned Thomson’s 1808 translation (which is still in print) Thomson’s translation omits the Deuterocanon, but includes Psalm 151, and follows the order of the Hebrew canon. His work was based indirectly (through J. Field’s 1665 edition and and the sixtine edition of 1587 on the well known fourth century AD manuscript Codex Vaticanus (B).
Brenton’s work, although it appeared some 35 years later than Thomson’s acknoledges only cursory and indirect acquaintance with it. As the title indicates, it too is (indirectly) based on Codex Vaticanus. Brenton mentions the Valpy edition of 1819 as his immediate source, which in tern was based on the Sixtine edition. Like Thomson, Brenton translated only the books of the Hebrew canon, plus Psalm 151, and ordered them accordingly. For Esher, however, he did not exise the Additions, as Thomson had done. However, I think you have not actually read the text, because Brenton includes notes throughout the text including variants from the fifth century Codex Alexandrinus (A), as well as comments on the Hebrew and Greek text.
Since then, however, our knowledge of the Septuagint text has advanced considerably. We’ve made advances in Greek lexicography and numerous ancient manuscripts have come to light. While thomson and Brenton were based on (essentially) diplomatic editions of a single manuscript, the critical edition of the Göttingen Septuagint of Genesis rests on a foundation of some one hundred and forty manuscripts (nine clearly predating the Codex Vaticanus.) Now, one thing you should know is that in developing the Göttingen Septuagint the editors drew on the Hebrew text, as the parent in the diglot, to help them with text critical decisions. Now the Göttingen Septuagint project will soon reach its anniversary mark, but the full completion of the Göttingen Septuagint probably will not occur for about a hundred more years.
Absent the Göttingen Septuagint, scholars general depend on Rahlfs 1935 eclectic text. This was the source used by the
Orthodox Study Bible (OSB) translators. The
New English Translation of the Septuagint (NETS) used Göttingen when it existed and in other cases used Rahlfs.
Now it is important to know that virtually no translation presents the Greek text as it appeared in the original. For example, rather than include a full translation of the
Book of Odes, which is a canonical text in the Greek, readers must refer to the original source material, namely (using their Greek names), Exodus 15:1-19; Deuteronomion [Deuteronomy] 32:1-43; 1 Reigns [1 Samuel] 2:1-10; Psalms 118:12, 144:2;Prayer of Manasses [Psalm 151]; Ionas [Jonah] 2:3-10; Habakoum [Habakkuk] 3:2-19; Esais [Isaiah] 5:1-9, 26:9-20, 38:10-20; Daniel 3:26-45, 52-88; and Luke 1:46-55, 68-89, 2:14, 29-32. In this sense, there is NO (Orthodox) Septuagint translation into English today – although one can easily reconstruct the Book of Odes from other material in the Bible.
Now, one of the unique and good attributes of the
New English Translation of the Septuagint is that it translates different source material. Sometimes the Old Greek version is paired with the version by Theodotion, as in the case of Sousanna [Susanna], Daniel, and Bel et Draco [Bel and the Dragon]. Other times, the divergent texts of the great pandects Alexandrinus and Vaticanus are included, as in the case of Iesous [Joshua]. In the NETS, all the various divergent versions are translated. The usefulness for students of this act of simultaneous scholarly integrity and translational generosity can hardly be exaggerated. The books provided with multiple translations are: Iesous [Joshua] (Alexandrinus and Vaticanus for several chapters), Judges (again, A and B), 1-4 Reigns [1-2 Samuel & 1-2 Kings] (Old Greek and Kaige), Esther (Old Greek and Alpha), Tobit (GII/Sinaiticus and GI/Alexandrinus & Vaticanus), Habakoum [Habakkuk] 3 (majority text and the Barberini text), and Sousanna [Susanna], Daniel, and Bel and the Dragon (Old Greek and Theodotion). In Iob [Job], the Theodotionic additions from Origen’s Hexaplaric text are included in brackets. In Sirach numerous verses from the Greek II text (not the Hebrew) are included in brackets.
The translation is made by the leading
academic scholars in the area, and preceded the
Orthodox Study Bible by a year.