Thanks. I certainly appreciate your post and I’m a Catholic.
So it’s fair to say the oldest this fragment could be is A.D. 550?
You’re welcome, and your courtesy is profoundly appreciated. May God richly bless you.
The sources I read didn’t get that specific. The researcher who discovered the papyrus estimated it originated in the “third, fourth or fifth century.” Some experts agreed with him, while some argued for the earlier date.
Catalogue listing at http://www.trismegistos.org/magic/detail.php?tm=64320 for "Manchester, John Rylands Library Gr. 470" (which is our baby-- the initial subject matter of this thread) puts range of dates as AD 450 - 799
There appears to be only one [primary] researcher who asserts yet earlier dating, doing so on rather dubious grounds, for that individual apparently thought he saw;
The preceding [above] truncated & adjusted quote I'd copied from http://pyat.org/2015/01/09/dating-the-sub-tuum-praesidium-is-marian-veneration-apostolic/.
If the polemical note inherent within the opening sentence of that link be set somewhat aside, further down (and where I had lifted the quote) there is copy of what is alleged to be commentary of;
470. CHRISTIAN PRAYER.
Aquired in 1917. 18 x 9.4 cm. ? Fourth century.
PLATE I.
This prayer, written in brown ink on a small sheet of papyrus (the verso is blank), is probably a private copy ; there are no indications that it was intended for liturgical use. The hand, tall, upright, and pointed, with small blobs at the top and bottom of vertical strokes, is of a peculiar type to which I know no exact parallel. The α is of a kind more common in inscriptions than in papyri, and Dr. Bell suggests that the peculiarity of the script might be explained on the ground that it was a model for an engraver.
Mr. Lobel has pointed out to me that the hand resembles somewhat that of the letter of Subatianus Aquila (Schubart, Papyri Graecae Berolinenses, 35; cf. id. Paeleographie, p. 73) with its large and narrow characters; the ο, ι, and to a less extent the ε, are similar in both texts, but the peculiar [hand drawing of character] found in 470 is missing in the other, which on the whole is less decorative. Lobel would be unwilling to place 470 later than the third century. But such individual hands are hard to date, and it is almost incredible that a prayer addressed directly to the Virgin in these terms could be written in the third century. The Virgin was spoken of as Θεοτόκος by Athanasius ; but there is no evidence even for private prayer addressed to her (cf. Greg. Naz. Orat. xxiv. II) before the latter part of the fourth century, and I find it difficult to think that our text was written earlier than that (cf. art. ‘Mary’ in Hastings, Encyclopaedia of Religion and Ethics). "
If papyrus 470 truly be from mid-third century, as Mr. Lobel was apparently persuaded be in realm of possibility, it's doubtful, barring something more in full explicitly asserting certainty rather than possibility, that the earliest proposed date (AD 250) be among Mr. Lobel's contemplated/accepted latest possible date?