From Just Solve the File Format Problem
TeleDisk was an early PC based disk imaging program. It was often used to image floppy disks from other systems, notably IBM mainframes or DEC workstations
The file format provides for splitting disk images into multiple parts; in this case, the second part will have a .TD1 extension, the third .TD2, and so on. In practice split disk images are extremely rare.
- TeleDisk downloads here
- Format specification by Dave Dunfield here
- Some reverse engineering and pseudo-code here
- MESS source code for reading TD0 files