i was mostly basing it off of the panel that houses the switches behind the focus ring.
left to right: f/4L, f/4L IS, f/2.8L, f/2.8L IS
the one in the image looks thin and noticeably closer to to the focus ring than the zoom ring. i think that's about the only really tell tale difference that is visible from the angle we're given.

Yup, non-IS it is.








