Got sent a "mystery offer" email and this was the offer.
However i tried the code on another account (where I had been sent a different, 15% off mystery offer) and it worked there too. So I suspect it is a generic code.
***Only valid until midnight tomorrow (9/11)****
No idea if it works site-wide or just menswear.
Just keep in mind that items bought online cannot be refunded or exchanged in-store. Got caught out on a previous online sale where I purchased a shirt that ended up being too big, and they wouldn't let me change sizes in-store.