Fred MacDowell at On The Main Line writes regarding the Aleppo Codex:
The Aleppo Codex (כתר ארם צובא) was the possession of the Jewish community of Aleppo, Syria for centuries. It was regarded as a treasure, which is why it was called by them The Crown; הכתר or 'el-Taj. By tradition it was regarded as having been written (or rather vocalized) by the greatest Masorete, 'Aharon (ben Moshe) ben 'Asher, which is what a colophon page in the book claimed. Furthermore, it was believed that this was the very book which the Rambam consulted in writing his own sepher Torah, as recounted in Mishne Torah Hilkhot Sepher Torah 8:5.
Fred also points out in his article:
1) In the Mishne Torah the Rambam says that the shirah of parashat ha'azinu must be written on 70 lines in a Torah (fully in accord with massekhet sopherim, I believe, sorry no cite at the moment).
2) In the Aleppo Codex this is written on 67 lines.
This would seem reason enough to conclude that this wasn't then the codex used by the Rambam, even with the long tradition. However, pointed out eagle-eyed Goshen-Gottstein, there is a mistake. It says 70 lines in all printed editions of the Rambam. What about old manuscripts? Sure enough, in the most authoritative manuscript of the Mishne Torah (in Oxford's Bodleian Library, the Huntington 80 mss) it says 67 lines, not 70. (Why is this the most authoritative manuscript? Because this appears in it.
This 67/70 ambiguity regarding the lines distinguishing the codex/mesorah used by Rambam to write his sefer Torah reminds me of parashat Vayigash. In this Torah portion, there is also an ambiguity involving the 69 (or is it 70) souls who went down into mitzrayim with Yaakov.
Interestingly, Serach figures significantly to both the 69/70 "discrepancy" of souls in parashat Vayigash, and to the 67/70 "discrepancy" of lines in the codex/mesorah consulted by Rambam to write his sefer Torah. Serach is both one of the "souls" listed in Vayigash, and she is the soul to whom the mesorah was given according to Yalkut Shim'oni 64.
For some odd reason (probably because I just learned this word today on Yitz' blog, Israel At War), I am connecting the double x/70 discrepancies  with the concept of hanhaga הנהגה as well. Perhaps it's the 3 feminine letters hey ה in the word hanhaga הנהגה and the 3 seemingly "missing" or hidden lines of the mesorah which are aligning together in my mind.
Even more oddly, I am also connecting the whole x/70 dilemma with the double kaf כ of the cooper scroll of Qumran. The seemingly "missing (or hidden) 3" may correlate to the "hidden" intellectual attributes of chochmah, binah and da'at/keter, where the hebrew letter kaf כ likewise correlates to the sefirah keter - and to its 2 distinct partzufim (the double kaf כ) and 3 "heads" (the 3 letters hey ה). Significantly, hey ה is the hebrew letter representing actualized expression in the 3 forms of thought, speech and action. Kaf כ is the hebrew letter "able" to actualize "potential" expression.
Further following this "hanhaga, head and expression thread", Yitz writes of hanhaga:
The answer is that while God Himself is Ein Sof, He has created a place of interaction between Himself and humanity that is, for our sakes, bounded and defined. This place is called hanhaga -- and this is the realm within which we can make use of our understanding and knowledge.
Moreover, hanhaga is from the root nahag נהג meaning to vocalize directions for movement , to lead and to conduct . Important to the meaning of providing direction through vocalization, Serach is she, who through her voice, sang the words "Yosef is alive", which revived the spirit of Yaakov. In other words, Serach vocalized to direct the movement of Yaakov's spirit toward revival.
Taking all this together, Serach is critically linked to the meaning of nahag נהג , the root to the realm of Divine-human interaction, as well as to the x/70 ambiguity involving the Aleppo Codex (the mesorah) used by the Rambam. Moreover, the mystical voice of Serach holds the key to the mystery (כ) and expression (ה-ה-ה) of the mesorah; each corresponding to the discrepancies of 69/70 and 67/70 respectively. Serach is the connection between them all. Additionally, the combined gematria of the letters representing "mystery" (כ) and "expression" (ה-ה-ה) is לה 35, meaning "to her". In other words, to her (Serach) the mesorah was given.
I realize this entry is a bit chaotically put together at this point. Nevertheless, the thread of connection has been established. The idea remains to be more fully developed with further study.
 where x = 1 kaf (כ) and/or x = 3 letters hey (ה-ה-ה)
 Etymological Dictionary Of Biblical Hebrew, R' Matityahu Clark
 YitzD, Israel At War, Kabbalah 2: A Glimpse Of G-d
technorati tags: Torah Talmud Torah Judaism Kabbalah jewish mysticism mysticism Aleppo Codex mesorah masorah masorete Serach Rambam Maimonides Mishnah Torah Mishne Torah hanhaga