Over on Baidu (Facebook for China), a user with hardware connections just discovered a Microsoft prototype while looking for other tech things. It's claimed that this was an early Lumia 960 prototype, but take it all with a pinch of salt. It doesn't appear to be a hoax, but we also can't verify much else about the scribbled on claims shown below.

From the Baidu post (translated):

Landlord today Huaqiang North, was originally dig a x2 motherboard did not expect to encounter this:

This was posted via Twitter on the baidunokibar account.

The device shown would make sense as something a year on from the Lumia 950 designs. The latter came out in Autumn 2015 and so would have been started in terms of design around Spring 2014 and signed off for production purposes in January 2015.

The 'Lumia 960' - or whatever it is - could have been started, in design terms, in Spring 2015 and the decision to can it might have been taken in early 2016. It's all speculation, really, but the claimed Snapdragon 820 chipset sounds about right (it would have come out in the same time frame as the Elite x3) and the stereo speakers and aluminium build do follow current trends.

Who knows? Very interesting though. Note the milled out sections of metal to allow access to electronic test points on the motherboard!