Discovered in Egypt in 1952, P66 is one of the oldest substantial copies of any Gospel. The codex contains nearly all of John (chapters 1-14 are nearly complete; 15-21 survive in fragments). The handwriting is careful, the codex was meant for serious church use, and corrections in the same scribal hands prove the copyist worked from a careful exemplar.
Why this matters
Pushes the substantial text of John back to circa 200 AD. With P52 (~125), P66 (~200), and P75 (~225), John's text history is now traceable across the entire 2nd century.
Scripture references
John 1John 3John 14
Location
Bodmer Library, Geneva