Pretty recently. Like within the past 2 or 3 months I think.
There is no specific marking, other than the updated company logo. The previous ASG-1 revisions had the previous Aurisonics logo.
I've never compared them directly to the GR07. Based on what I remember they're cut from the same cloth though. Great bass, solid and slightly forward midrange, and highs that are rolled off. Perhaps someone with more recent knowledge of the GR07 and the ASG-1 can chime in.
Personally if you have the GR07 I'm not sure that I'd give up the MadDogs for the ASG-1.3s.
Don't forget that the shell is also slightly different on the 1.3. The nub at the top of the ear is now less prominent so it should fit more comfortably into peoples ears. The ASG-1.3 can also be identified by it being the only ASG-1 model to include space near the bottom of the nozzle for it to be quickly upgraded to the ASG-2.
Those are the main ways to indicate that you have a 1.3 versus any other revision, though the logo change is a key difference that's the easiest to tell