There’s a western-style cut to the two front pockets of this green shirt, which both sit on an subtle angle, rather than lying straight across the chest. Other than that, it has multiple decorative seams and does up with snaps, not buttons, which isn’t Dean’s usual preference.
In Girls Girls Girls (10x07), Dean wears this shirt from the beginning of the episode until after they find the corpse of the demon at the brothel.
In The Things They Carried (10x15), Dean wears this shirt at the beginning of the episode when he convinces Sam to go on the case.
In Brother’s Keeper (10x23), Dean wears this shirt when he goes to the vamp nest and gets Rudy killed.
In Our Little World (11x05), Dean is wearing this shirt when he comes back to the motel after disposing of the demon’s body. He wears it until his encounter with Amara.
In Don’t You Forget About Me (11x12), Dean wears this shirt from the beginning of the episode until after the dinner with Jody and the girls in Sioux Falls.
In Mamma Mia (12x02), Dean wears this shirt at the beginning of the episode, when he talks to Cas on the phone and has a brief conversation with Mary.