I usually wear a medium in gitman vintage, and got a couple shirts in a small from a stockist recommendation. My suit size is usually 40", true chest size is 39". 5'7", 145lbs. The grey speckled traveler shirt is made from fabric that is pretty heavy (similar to the japanese nep dungaree shirts from W+H, but heavier) so I returned it cause it'd be too heavy to wear during the summer months. The polka dot rebel shirt is pretty awesome, as well as the sun faded red shirt. I believe the TS shirts in small translate pretty well to GV mediums pretty well. If anybody is interested in fit pics, I can post a couple.