What is it?

“For a humble piece of papyri it became as important a find for New Testament scholarship as the Blue Diamond of India!"

Larry Hurtado BA MA PhD FRSE Emeritus Professor New Testament Language, Literature & Theology. New College, Edinburgh

In 1934 in the Ryland's library in Manchester university, Colin H. Roberts was looking through a pile of what was essentially thought to be rubbish and he found a fragment of papyrus. Roberts noted that due to there being text on both sides it was part of a codex and not a scroll. Christians had popularised the use of codexes since AD 90 and so there was excitement that this could be a significant New Testament find- and so it proved. The small piece of papyrus turned out to be fragments of John's Gospel, chapter 18:31-33 and 37-38 respectively.
Roberts contacted leading palaeographers (The study of ancient writing) regarding the dating of P52 and they subsequently dated it between 100 and 150CE; This makes P52, even at the latest dating, the earliest Christian manuscript to be found.
Roberts was keen to have P52 dated to a similar time as the Egerton Fragment as this had been dated to the end of the first century. Egerton has since been dated later calling into question the earlier datings of P52. As palaeographic dating has an error margin of around plus or minus 50 years it makes precise dating almost impossible.
p52aboveegerton

P52 above a piece of the Egerton Fragment. As you can see the style of writing is not dissimilar to P52, making it possible for them to be dated closely together.