Microsoft appears to have begun issuing builds of Windows Phone 10 to select partners outside company walls. According to our sources who are close to the matter, the build issued to partners is a fairly old build, and doesn't include any on-the-surface features. However we can confirm that the build being issued out to partners is branded as Windows Phone 10.
Considering the build issued to partners is fairly old, and since Microsoft is yet to publicly announce any plans for the phone side of Windows 10, we're not entirely sure how Microsoft plan to market "Windows Phone" with Windows 10. Will they stick with Windows Phone 10 (as that's what the operating system is branded as in these early builds), or will they simply call it Windows 10, running on the phone?
WinBeta is unable to identify any new features within the build, as it looks like this build is very similar, if not almost identical to Windows Phone 8.1 with Update 1.
It's great news however that Microsoft has finally started focusing more on the phone side of things. Up until this point, all work being done on the phone was internal. Hopefully this means Microsoft is gearing up to talk more about their plans for phone, as recent rumors claim the company is planning to release a preview of Windows 10 to the public which runs on phones and tablets in the new year.