This shirt, of course, is different from Sam’s other blue and yellow plaids... because he likes to make my life difficult. It does up with buttons and has two breast pockets with flaps, and is not cut in the western style (as is usually typical of Sam’s shirts). The plaid pattern is a medium plaid that I think has a weird visual illusion of being an irregular pattern at first glance (also, I just needed a new word in the title that would be distinctive).
Brand: Lucky Brand
In Thin Lizzie (11x05), Sam wears this shirt in his first scene in the Bunker, when he tells Dean about the case. He keeps it on for the trip to Fall River and their initial investigation there – until the second murder occurs.
In Into the Mystic (11x11), Sam wears this shirt while they guard Mildred and wait for the banshee to strike.
In The Chitters (11x19), Sam wears this shirt when he meets Dean at the bar and is introduced to Cesar and Jesse. He wears it for the rest of the episode.
In The One You’ve Been Waiting For (12x05), Sam wears this shirt until they have finished their investigation of the antique shop. And then he changes.
In The British Invasion (12x17), Sam wears this shirt at the beginning of the episode when he and Dean come back to the Bunker with takeout and find Mick waiting for them.
In Scoobynatural (13x16), Sam wears this shirt when he’s researching cursed objects in the Bunker, and Sam calls him into another room to show him where he put the TV – he is then sucked into Scoobydoo and this shirt gets cartoon-ified. He wears it for the rest of the episode (except a brief scene when he is in cartoon PJs in the mansion.)