Before Microsoft acquired Nokia, the company was heavily rumoured to be working on its own in-house Windows Phone device that was expected to ship in 2014 under the Surface moniker alongside its Surface Pro device. The build of Windows Phone that it’s running appears to be from September 2013, and is from an internal development branch building towards what eventually became Windows Phone 8.1. Real images of this mysterious Windows Phone prototype. The Surface Phone we eventually got arrived as the Surface Duo, which started development in 2016 and launched to the public in 2020. In that time, Microsoft shipped Nokia designs in the form of the Lumia 640, 650, 950, and 550 running Windows Phone, before abandoning the platform in 2017.