In the latest issue of the Oxyrhynchus Papyri series (LXXVIII, Egyptian Exploration Society, 2012), W. B. Henry offers an edition of P.Oxy. 5129 (Justin Martyr's First Apology), which is the earliest Greek manuscript of any text of Justin Martyr. According to Henry, "[t]his is the first published ancient copy of a work of Justin Martyr. The text is otherwise known only from the unreliable manuscript A (Parisinus graecus 450, of 1364)." Henry dates the hand to the 4th century CE, citing P.Oxy. 2699 and P.Herm. 5 as comparanda. This is, therefore, an incredible discovery, since P.Oxy. 5129 predates the earliest manuscript of Justin by a millennium! There are a few variants in the fragment (e.g., omission of εντυχειν in 50.12, υμων instead of ημων in 51.4) that make the text important for text-critical study of Justin's First Apology.
The manuscript is written on parchment in an elegant hand of the "Severe" type. Unfortunately, only six, partial lines have been preserved (3 lines on hair, 3 lines on flesh), and the flesh side is particularly sparse. Henry collates the text with the critical edition of D. Minns and P. Parvis (2009). For interested readers, I reproduce Henry's transcription of the text of P.Oxy. 5129 below, alongside my own translation (with brackets signifying reconstructions), which is followed by a snapshot of the hair side of the fragment.