When Dean gets back from Hell, he doesn’t have access to his own wardrobe. He shows up at Bobby’s doorstep in very dirty clothes, but once he convinces Bobby that it’s really him – he has a shower, and changes into this shirt of Bobby’s. It’s Tan, not a usual Dean Winchester colour of choice. It’s a thicker material, with two breast pockets that have a centre pleat in them. It does up with buttons.
Brand: Eddie Bauer
Dean puts in on in Lazarus Rising (4x01), after he’s convinced Bobby that he’s not a demon or shifter, and he’s thus gained access to a shower and borrowed clothes. He wears it until he and Bobby track down Sam. He changes out of it after Bobby leaves to call Pamela and Dean tells Sam that he doesn’t remember Hell.
FATE: Returned to Bobby, as we can see in Yellow Fever (4x06) when Bobby is wearing it: