Mount reiserfs .dsk image failed: can't read superblock

I have a failed 160 GB Western Digital Netcenter NAS disk and its image after failing in .DSK format.

When I connect the disk to my ubuntu machine and typed:

# losetup -o 512006144 /dev/loop1 /dev/sdc      
# mkdir /tmp/sdc
# mount -r -t reiserfs /dev/loop1 /tmp/sdc

I get my folders and files in the /tmp/sdc folder then I can copy some files and folders but at a very slow speed.

When I try to get them from the .dsk file with:

# losetup -o 512006144 /dev/loop2 /media/wdnas.dsk      
# mkdir /tmp/dsk
# mount -r -t reiserfs /dev/loop2 /tmp/dsk

In the mount command I got:

mount: /dev/loop2: can't read superblock

How can I fix that?

I compared the disk content and the .dsk file in a hexadecimal editor and they look the same!