At his Patheos blog, Michael Bird recently cited a lengthy portion from Helmut Koester’s History and Literature of Early Christianity where Koester argues that 2 Timothy (which he takes as pseudonymous) was written from Philippi. After mentioning the various locations Paul refers to in the latter part of the letter, Koester states, “Any glance at a map will show that he thought of Paul as imprisoned in Philippi.” He is not mildly suggesting. See the full section at Bird’s blog.
This depends on the pseudonymity of the letter, of which I am not convinced, but it is intriguing to see this argument. It would be interesting to connect this with the work of Peter Walker who has made fresh arguments for placing the PE within the chronology.