According to the report, Windows Central obtained the video via internal and external sources which wish to remain anonymous. In the video, we see many interesting ideas that Microsoft had planned for the Lumia 950 series, which never reached the market.
For instance, the Lumia 950 and the Lumia 950 XL were supposed to have a pen, as well as a Smart Cover. A pen surely would have made the Lumia 950 series more competitive against other smartphones of its era, such as the Samsung Galaxy Note 5.
Furthermore, the pen looks a lot like the Surface Pen which has become one of the most important accessories of the Surface devices. In the video, we also see the pen working in OneNote on Lumia 950, a function that never made it into the product.
Concerning the Smart Cover, the video doesn't show the accessory. However, according to the sources of Windows Central, Microsoft included it in its initial plans. The Smart Cover would have been sold separately, giving users Glance Screen access at the top half of the display when the cover was closed.
“3D Touch” and different design
Of course, Microsoft had more features for the Lumia 950 series that it never released to the market. Apparently, the company had plans to include the famous “3D Touch” feature in the Lumia 950 series.
This might sound familiar and it is, thanks to the Nokia Lumia McLaren. Microsoft and Nokia co-developed the smartphone but never released it. Lumia McLaren's top feature would have been “3D Touch”. It would have allowed the user to interact with the phone using gestures.
Finally, the video features small differences in the Lumia 950 design. These differences are probably because the phones in the video are mostly concepts.