Update - Tom Warren and others are now saying this is just a Lumia 1520. Nothing to see here, folks.
Rumors of a mid-range Lumia phone codenamed 'Tesla' have been circulating for a few weeks now after first being revealed by @evleaks in June. The phone is reportedly destined for AT&T and it should fit nicely into a high-end but mid-range phone (that may sound contradictory, but if you think of what a Lumia 820 is, it's not).
Now, a new image of Tesla – that may either be known as the Lumia 730 or Lumia 830 – is making the rounds, sporting the new Update 1 OS refresh for Windows Phone 8.1. Not much is known about this device yet, although it reportedly will get PureView camera status, a first for this range of device as Microsoft pushes the technology down their Lumia line.
This photo is not the first time we have seen Tesla, as three photos showing off the squarish phone came out on July 3rd. The phone's design is clearly inspired by the Lumia 630 and Lumia 930 series with the square edges, although this leans towards the 930 a bit more with the metal band. The PureView camera, with a housing influenced by the Lumia 1020, is also visible on the back.
No word on when Tesla may hit AT&T (or other carriers globally) besides the third quarter, though presumably as Update 1 for Windows Phone 8.1 begins to make its way out into the wild, more news will be forthcoming.
There is still another Microsoft phone reportedly coming out called 'Superman,' a possible Lumia 730 device for Verizon with a 5MP front-facing camera, according to the Verge. A recent selfie by Microsoft's Joe Belfiore is speculated as being shot with that mystery phone.