Windows 10 Version 1511 (Build 10586), codenamed Threshold 2
Specifically:
Universal Windows Platform (UWP) apps like Mail, Calendar, Photos, and OneNote received design refinements and better performance. The Calculator app finally got unit conversion and date calculation features. windows 10 version 1511 build 10586 iso
Always verify the SHA-1 hash of any ISO you download against known official values. Corrupt or tampered ISOs can contain malware. Windows 10 Version 1511 (Build 10586), codenamed Threshold