Winger, Thomas M. "Introduction: Location and Date of Writing." Ephesians. St. Louis: Concordia Publishing House, 2014, 122-130.
In Ephesians 6:20, Paul states that he is a prisoner. Winger briefly discusses the significance of the imprisonment of an ambassador. Though all creation recognizes the Creator, the earthly kingdoms may not, and feel free to mistreat God's ambassadors (Winger 2014, 122). Winger observes that five letters of Paul are identified as Prison Epistles: Ephesians, Colossians, Philemon, Philippians, and 2 Timothy. "The first three are united, first, by geographical proximity of their destinations in the Lycus-Meander Valley and, second, by their letter carrier" (Winger 2014, 122). Colossians and Philemon both mention Archippus and Epaphras, along with Tychicus, who accompanies Onesimus to Philemon. Paul tells Timothy (2 Tim. 4:12) that he sent Tychicus to Ephesus. Winger takes this as a reference to the delivery of letters, including Ephesians (Winger 2014, 123).
Winger finds strong arguments that Paul's imprisonment while writing the Prison Epistles was in Rome. By the 4th Century, major manuscripts add that the letter is "from Rome" (Winger 2014, 123). Paul's relative freedom described in Acts 28 would have allowed for letter writing as well as receiving and sending people.
There is some speculation that Paul was actually imprisoned in Ephesus at the time of writing (Winger 2014, 124). Though this is possible, Winger doubts whether Onesimus could have hoped to disappear in Ephesus. Mark and Luke are also not known to have been with Paul at Ephesus (Winger 2014, 125).
Paul was known to be imprisoned in Caesarea for two years (Winger 2014, 125). There may be reasonable chances that Onesimus would flee there. The imprisonment in Caesarea apparently involved some level of freedom (Winger 2014, 126). Paul's desire (Philemon 23) to visit Philemon on the way to Rome and Spain makes geographical sense. Further, some of the claims which led to Paul's imprisonment in Caesarea stemmed from conflicts in Ephesus, which had followed him to Caesarea. This could reasonably spur an encouraging and clarifying letter from Paul to Ephesus (Winger 2014, 127). Caesarea, at the time, like Ephesus, was experiencing significant turmoil between Jewish and Gentile factions (Winger 2014, 128).
Winger continues to discuss the time period of the Caesarean imprisonment as a time which fits the issues raised in Ephesians. Not only do matters of Jewish and Gentile background fit the timing, but also issues of citizenship were at the center of debate (Winger 2014, 128). Paul's concern with the feast of Pentecost also suggests his deliberate timing when he went to Jerusalem and was arrested. Winger notes that in the probably thinking of Paul, Pentecost would be connected to the giving of the Mosaic Law, suggestive of Ephesians 4:25-29, 6:2,, 4:7-16, 1:20-23, 2:6, 4:7-16, and 1:20-22 (Winger 2014, 129). Pentecost was also seen as the occasion of Israel's marriage with God through the Law, suggesting a tie to Ephesians 5:21-33. Finally, the work of the Holy Spirit is related, suggesting Ephesians 5:18.
Winger thus concludes that Ephesians was probably written from prison in Caesarea, early in his time there, probably around A.D. 52, based on the Gallio Inscription and Acts 18:12 (Winger 2014, 129). However, Winger does not consider the Roman imprisonment to be impossible, and his commentary allows for such a scenario (Winger 2014, 130).