While very similar to Dean’s original Marine Blue Shirt – with its matching buttons and colour – this shirt has a slightly different cut to the pockets.
In Torn and Frayed (8x10), Dean is wearing this shirt while napping at Rufus’ cabin. Cas surprises him, making Dean accidentally spill bear all over himself. He then changes.
In Heaven Can’t Wait (9x06), this might be the shirt that Dean wears when he tracks down Cas at the Gas’n’Sip until the end of the episode.
In First Born (9x11), this might be the shirt that Dean wears for the entire episode.
In King of the Damned (9x21), this might be the shirt that Dean wears from when Crowley calls about Abaddon until the end of the episode.