Let’s check x64frev in hex:
Type dism /Get-WimInfo /WimFile:F:\sources\install.wim /index:1 (Replace F: with your USB drive letter). This will reveal the "friendly" name like .
: Only download ISOs with these names from official Microsoft sources (like the Windows Insider page). Third-party "ces" builds may contain malware or unauthorized modifications.
As of today, in mainstream computing. It most likely represents: