This is a cardigan from J.Crew that I'm calling Lightweight Short-Sleeve Cardigan (item #16932), which retails for $49.50. I saw this in-store in this color, stone, and I don't recall seeing any other ones (but admittedly, I didn't really look for any). This sweater is alpha-sized. I tried this sweater on in a size small, in the stone color.
I left this sweater behind because I was not on a buying trip. I wasn't a huge fan of the way the buttons pulled, but other than that, I liked this sweater. It is a nice, lightweight sweater that can be styled various ways, and is reasonably priced, especially for J.Crew.