The disks in this directory are taken from the fsck.technology NeXT Applications repository.

They have been modified by removing a 46-byte header that prevents them from being loaded in old versions of the Previous emulator (< 3.9).

A valid NeXT floppy image starts with the bytes 64 6c 56 33 (ASCII "dlv3")

The header is added by DiskCopyII.app, as explained in these posts:

https://www.nextcomputers.org/forums/index.php?topic=4581.msg26737#msg26737
https://www.nextcomputers.org/forums/index.php?topic=4581.msg26713#msg26713