Codex Ephraemi Rescriptus
The Codex Ephraemi Rescriptus is a manuscript of the Greek Bible, written on parchment. It is designated by the siglum C or 04 in the Gregory-Aland numbering of New Testament manuscripts, and δ 3 in the von Soden numbering of New Testament manuscripts.
Source: Wikipedia — Codex Ephraemi Rescriptus (CC BY-SA 4.0)