Eustathios 23 was a myster(iakos?); owner of a seal dateable to the eighth or ninth century: Schlumberger, Sig., p. 545, no. 1 (facsimile). Obv.: invocative monogram of Κύριε βοήθει. Rev.: Ευ - σταθ - ιῳ μυς - τερ(ιακῷ) (?). His title is uncertain and his functions unknown.

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