Heidegger's Bible Handbook: Galatians: Subscript
2. The Subscription disapproved. It appears to have been written, not at Rome, but at Ephesus.
The Subscript reads: ἐγράφη πρὸς Γαλάτας ἀπὸ Ῥώμης, written to the Galatians from Rome. So also the Arabic and Syriac. The Arabic adds that this was sent by Timothy. Nevertheless, these things are not sufficiently proven. For, if, as we shall afterwards show, this Epistle was written near the end of the two year period at Ephesus, it was not able to be written at Rome, since about that time the Apostle did not see Rome. But it is trifling, what some think, that in Galatians 6:17 by the marks/stigmata are understood those things that he suffered at Rome, althought they are equally able to be understood of the blows and stripes that he suffered before coming to Rome. Therefore, some affirm that it was more probably written at Antioch after Paul’s second journey: others, at Ephesus after the third.