A Koine dvandva

DGE, but not LSJ (or the Rev.Supp.), has an entry for Διονυσο-πλάτων referring to a signet ring with a depiction not only of Dionysus (note the name of the witness and of his father), but also of Plato thereon: 'Dioniso-Platón, representación de Dioniso y Platón'.

The eighth of nine witnesses to P.Oxy. I 105 (118-138 CE) wrote/had written (lines 19-20): 
Διονύσιος Διον[υσ]ίου τ[ο]ῦ Διογένους ἀπὸ τῆς αὐτῆ[ς] πόλεως
μαρτ[υ]ρῶ[τῇ τοῦ Πεκύσιος διαθήκῃ, καὶ εἰμὶ] ἐτῶν τεσσαράκοντα ἕξ, οὐλὴ παρὰ κρόταφον δεξιόν, καὶ ἔστι μου ἡ σφραγὶς Διονυσοπλάτωνος.

The translation in the ed.pr. stops before the details of the witnesses...