In the documents, Microsoft refers to its project Andromeda as something that they have been quietly working on for a long time, which will create a totally new and disruptive device category. It's supposed to be released this year, so expect it to appear somewhere this Autumn.
Then, less than a month ago, Thurrot published info from reportedly leaked documents saying Andromeda could make an appearance as soon at this year, alongside Libra, a smaller, low-priced Surface, and Carmel, the next version of the Surface Pro. The Surface Pro has been successful on that front, and some companies - even Apple to an extent - is clearly emulating Microsoft's strategy now.
From the sound of things, this dual-screen device isn't a Surface by way of the Nintendo DS.
Another important detail obtained by The Verge is that the display will extend over the length of the front face of the newfangled gadget, and over the hinge when the device is fully open to present a almost seamless single display, as opposed to two separate displays just held together by a single substrate.
The idea is to blur the lines between computers and smartphones, much as the original Surface blended elements of notebooks and tablets.
The Verge notes that Microsoft's "current engineering samples" resemble 3D concept art created by the Austria-based designer David Breyer, who used existing patents as a guide. Microsoft has also reportedly been working on stylus input for the device, so that users can unfold it and write in it like a book.
It's possible Microsoft could choose to launch the device alongside the next major Windows 10 Update, likely to be called the Fall Creators Update 2018, this September.