Final answer:
The Beowulf manuscript is found in the Nowell Codex, part of the Cotton Vitellius A. xv in the British Library.
Step-by-step explanation:
The Beowulf manuscript is contained in a historical codex known as the Nowell Codex. Specifically, this codex is part of a larger manuscript, which includes other texts and is often referred to as the Cotton Vitellius A. xv. This is because it is housed within the Cotton collection of the British Library, catalogued under the name of its one-time owner, Sir Robert Cotton, by the unique shelfmark of Cotton Vitellius A.xv. The Nowell Codex, which contains Beowulf, is not to be confused with the beautifully illustrated manuscripts like the Lindisfarne Gospels or the Hillinus Codex, which represent other forms of medieval artistic illumination and codex production.