Heidegger's Bible Handbook: 2 Corinthians: Subscript
3. The Subscription. That the Epistle appears to have been written in Macedonia, and to have been sent by Titus and Lucas.
That this Epistle was written ἀπὸ Φιλίππων τῆς Μακεδονίας, διὰ Τίτου καὶ Λουκᾶ, from Philippi of Macedonia, through Titus and Lucas, the common subscription has it. In a certain, most ancient Codex, in the place of διὰ Τίτου καὶ Λουκᾶ, through Titus and Lucas, is found ὑπὸ Παύλου καὶ Τιμοθέου, by Paul and Timotheus. But in Codex Claromontanus it is read in yet another way: Ἡ πρὸς Κορινθίους β. ἐπληρώθη. Ἄρχεται δὲ ἡ πρὸς Γαλάτας, the second to the Corinthians is finished: the Epistle to the Galatians begins. Nevertheless, that former and common subscription appears to be worthy of preference, because it is probable that it was written in Macedonia, in which Philippi was, and that it was sent through Titus and Lucas, concerning which below.