Jon Hamm was back in his bulletproof vest Saturday to continue work on The Town in Boston. He was joined by costar Ben Affleck, who took a break from his fun times with Jennifer, Violet, and Seraphina for the afternoon on set. Jon was a little more dressed up earlier last week to appear on The Late Show — the video's below the jump. He and Dave chatted about the new project with Ben, as well as a little about his baseball-playing past. They also touched on Jon's work with Mad Men leading up to another exciting episode last night. Plus ICYMI, check out his costar Christina Hendricks's weekend wedding!

To see a video of Jon on Letterman, just