P. Ross. Georg. 2 18
Attestation in Greek:
Line 141: [ethnic]
Context (Duke): [...]ὶ Θερμουθαρίῳ … ὁ δεῖνα … Ἀντινοεὺς διὰ Μαρκίωνος Ἱερωνύμωι Απ… καὶ τῷ δεῖνι [...]
"... Antonite (i.e. resident of Antinoopolis) through Marcion of hallowed names ..."
or alternatively
Mr. X from Antinoe makes a contract with Hieronymos and another party through the intermediary of Marcion.
Marcion is in the genitive form in the fragment. It is impossible to know what the original meaning of the full sentence was.