That 2015 ISO — which Microsoft called the "last version of Windows" — was quickly followed by 1511 (November Update), then 1607 (Anniversary Update), then 1703, 1709, 1803… So much for "last version."
Officially designated as the "Windows 10 November Update" was actually version 1511; the July 2015 release was simply the "Initial Version." It introduced the core elements that defined the Windows 10 era: windows 10 version 2015 iso