Josephus tells us (Life, § 75) that Titus brought away with him from Jerusalem the codices (or manuscripts) that were in the Temple. These were among the spoils he took to Rome, and were deposited in the royal palace, about A.D. 70.
About A.D. 220 the Emperor Severus, who built a synagogue in Rome which was called after his name, handed over the codex of the Pentateuch to the Jewish community.
Both codex and synagogue have perished, but a list of thirty-two passages is preserved in the Massorah, wherein this codex differed in letters and words form other codices. There are two lists extant : one (prior to A.D. 1280) in the possession of the Jewish community of Prague, and the other in the Paris National Library (no. 31, folio. 399a). But there are other Severin preserved, which are noted in the margin of this edition.
The following is the complete list. Those that affect the sense
and furnish instruction are referred to in the margin, in notes on the
passages affected. Some of them relate only to spelling, and have
no instruction in them. (For further information see Ginsburg's
to the Hebrew Bible, pp. 409-20.)