Windows NT 3.5 build 683

Windows NT 3.5 build 683.1 is the official Beta 2 build of Windows NT 3.5, mentioned in the file  from Windows NT 3.50.854.1.

The Workstation edition of this build was leaked by a warez group in 1994, but the floppy disks were mistakenly dumped in 1.44MB format instead of DMF (1.68MB), resulting in unrecoverable data loss. This means most of the disk images are broken and the build is unusable.

The Server edition was also scene leaked at the time, as it's mentioned in a warez CD list, but remains to be found. It was supposedly leaked on the Chinese site BetaWorld on 2019-10-19, but this cannot be confirmed as it's not publicly available. Bootdisks for this build are available on BetaArchive.