The two .nib files are protected images from the original master disks.
The two .dsk files are the patched images. The sector patches are listed below.

On Merlin disk side A:

Sector edit track $03 sector $07 byte $48 from $EE to $2C and bytes $6F,$70 from $D0 $FA to $A9 $00
Sector edit track $14 sector $00 byte $C4 from $EA $EA $EA $EA to $8D $06 $C0 $60

These sectors are in the file: ASM.OBJ