I have a few items, and there are some slight changes over the years, also depends if it is YSL or Saint Laurent or the Rive Gauche line (which they seemed to have revisited) and where it was manufactured, this one seems to be from the Saint Laurent line and I checked a few tags (well only 2, as they were closest), doesn't look strange, but you want to check the material label
The labels are vary a bit, seriously, nothing screams fake at me, where did you buy it from? If you are seriously so worried, I would order from their website or NetAPorter, etc
Thank you! I found 3 tshirts on Rebelle.com that have the same label except for the stitching in the neck so I am relieved.