For a while, rumors were circulating that Microsoft was working on McLaren -- a successor to the Lumia 1020 with a giant camera and "3D touch" gestures. It was supposedly cancelled, but a listing for a prototype on Chinese auction site Taobao suggests that the device was close to completion.
Known only by its internal RM-1052 name, the Windows Phone has a 1020-like camera hump and similar styling cues, but it's made mostly of aluminum. There's only a hint of plastic at the bottom that's presumably meant to improve wireless reception.
The mystery phone appears to have superior performance, too, since a software shot points to a 1080p screen instead of the older phone's 720p panel.
The camera doesn't appear to have a mechanical shutter, and it looks like there's a conventional LED flash instead of xenon; either Microsoft was planning to scale back the optical technology on McLaren, or this is another device entirely. If it's the latter, there's still a chance that this represents a future product, rather than a vision of a Lumia that might have been.