This shirt is actually plaid, but the horizontal lines are so bold that it might as well just be a horizontal striped shirt. It’s plain cut and does up with buttons. It has two breast pockets that also have buttons, but no flaps.
Brand: Stapleford (Parker)
In Into the Mystic (11x11), Sam wears this after waking up from his disturbed sleep at the beginning of the episode. He changes out of it when they put on suits to go investigate the case.
In Lily Sunder Has Some Regrets (12x10), Sam wears this shirt at the beginning of the episode when they are in the Bunker, and in the car as they travel to the scene of Benjamin’s death.
In Twigs & Twine & Tasha Banes (12x20), Sam wears this shirt at the beginning of the episode when they are in the Bunker worrying about Castiel, and he gets the call from Max and Alicia.