NDIF
From Applepedia
NDIF (New Disk Image Format) is Apple's previous format for disk images (it has been replaced by DMG). When it was introduced it supported checksums and transparent compression, in contrast to the earlier Disk Copy 4.2 format. It is supported in Disk Copy 6 and later. NDIF files can also be embedded in self-extracting archives.
NDIF files store disk meta-data in the resource fork of the file, so if you transfer it through a system that doesn't support resource forks, it will be corrupted beyond repair. Always put NDIF files in a StuffIt, MacBinary or BinHex archive.

