This very broad grey and blue plaid does up with snaps. It’s got very broad stripes and when Sam wears a jacket, it’s the horizontal stripes that stand out the most.
Brand: American Eagle
In Slash Fiction (7x06), Sam is wearing this shirt when he and Dean leave Frank’s house and travel ultimately to Ankeny, Iowa. He wears it until the leviathan doppelgangers are dispatched.
In The Executioner’s Song (10x14), Sam wears this shirt at the end of the episode when it’s the morning after and Sam’s trying to convince Dean that everything will be okay.
Worn by Jared: Chicago Salute to Supernatural Convention 2012 (see comments)