Digital preservationists have uploaded verified copies of the original MSDN (Microsoft Developer Network) ISOs to the Internet Archive. When downloading from third-party archives, always verify the SHA-1 or MD5 hash values of the file against known Microsoft MSDN hashes to ensure the file has not been modified with malicious code. Original 2015 File Details for Verification:
If you have a paid subscription, Microsoft provides an archive of every Windows 10 version in the "Downloads" section. Volume Licensing Service Center (VLSC): windows 10 version 2015 iso
If you have an active MSDN or Visual Studio Enterprise subscription, you can download original Windows 10 ISOs, including version 1507, from the subscriber downloads portal. including version 1507