Loeb Classical Library description of the Codex Memmianus (the oldest extant manuscript of Suetonius' Lives of the Caesars).
K. R. Bradley, "Introduction," Suetonius, Vol. 1: The Lives of the Caesars, translated by J. C. Rolfe, (Harvard: Cambridge) 28, 1914.
M: Codex Memmianus (Paris, lat. 6115), the oldest extant manuscript, written at Tours ca. 820 and apparently with no direct descendants. It contains corrections subsequently made by another hand (M2, not later than the twelfth century), and of the two classes of manuscripts into which the tradition divides, X and Z, belongs to the former.