Hi again, v-drome! Yes, you found it. It is a problem-free "Eleutheriou"
monogram.
For your information, you proposed T and C as well: there's not T, and C would have to be implicated in theta. This is a possibility, but it is not the convention. If there
had been a C in the name, it would have appeared somewhere in the
monogram by itself.
Also, the date seems to be 6th century to me. 5th is too early. Possilby early 7th.
Regards
Gert