What Is the Samsung Serrano, and What’s Its Relationship to the Galaxy S 4?

In the time leading up to the launch of the Galaxy S 4, we sure heard plenty of rumors about just what sort of hardware we’d end up seeing. You might remember that a “Project J” was mentioned more than once. Supposedly, the GS4 itself was the main Project J model, but a number of others were mentioned. Specifically, we heard about both a J Mini and a J Active. A GS4 Mini sounded about right, but at the time we didn’t quite know what to make of the Active; recently, evidence of a waterproof GS4 Active has finally turned up to answer our questions. Today, we add to the Project J story with a rumor claiming that a “third Project J handset” is coming to AT&T.
This model may be called the Samsung Serrano, unless that’s just another codename; the phone’s model number should be SGH-I257.
So, how would this relate to the Galaxy S 4? That bit about it being the third Project J model is a little confusing, as we already heard about the GS4, Mini, and Active under the Project J umbrella; perhaps Serrano will be the third Project J model in addition to the original GS4. Maybe it’s even actually the Mini – we’ve yet to hear that announced, but then again it would seem odd to drop the GS4 part from its name.
The model number, at least, has us thinking this could be a distinctly lower-end Android than the GS4 proper.
Update: That Serrano name has been attached to the GS4 Mini in the past; if this is indeed that model, it would make a lot of sense.
Source: evleaks (Twitter)