Also see PhysOrg.com's article, Lost Roman law code discovered in London.
The Encyclopedic Dictionary of Roman Law (1953) defines the Codex Gregorianus as "the earliest private, systematic collection of imperial constitutions, published not before 291 by an unknown author (Gregorius?). The oldest constitution is by Hadrian. The Codex Gregorianus is not preserved and is known in excerpts only...." Since there are now more than excerpts, this discovery changes the working definition of the codex.
The fragments that were put together appear to be written in what are called Rustic Capitals (actually, only the title), the script in the accompanying Vergil manuscript, which I'm using because I don't have permission to use the Gergorian Code photo. Rustic capitals for vellum or papyrus were distinguished from the Square capitals used in inscriptions.
Photo credit: Vergil Portrait From the 5th C. Vergilius Romanus Manuscript
Public Domain. Courtesy of Wikipedia.

Comments
I’d read that some laws were written on bronze tablets, but they only have a few examples.
Early Christians tended to destroy anything “not approved” or coming from recognized authority. Many laws were written on tablets and metals, but recycled at some point.
Does anyone know what happened to the Twelve Tables set ot on the Forum? I could not find out online.