Thank you for your comments. I believe the letter in question in line 1 is inscribed like a μ (miniscule mu) — a very common form on late inscriptions (and of course on papyri). I’m reasonably certain of the reading of the first and second lines. There are several examples of this formula in Christian literary sources.

I’ll have to think some more about your suggestion for line 3 — it looks quite promising. However, if right, it makes the ουτ(-) or θυτ(-) that follows very enigmatic.

I believe you have solved the riddle of the beginning of line 5. In fact, I now see the lower horizontal of the delta. I would now restore something like:

[- - - - - - - - - lei]tourgesantos
[presb(uterou) kai/ke p]eriod(eutou). etous Π??.

As for the year, πω would yield 880 (= A.D. 568/9), not 890, right?

I wonder whether the second letter might not be a phi, so we have ΠΦ = 580. But then there would be two traces after this. Could these two traces be the abbreviation i(ndiktionos) ι’? The overline over these last two traces also seems to be higher, perhaps indicating they belong to a different dating system.