I found this at CDRlabs.com. Thanks to Ian.
Unique Features of LTD166S
- User protection against fragment of crashing disc :
- New top cover with folding edge
- Acoustic noise improvement
- No damper screw hole on tray
- Stream-line design of chassis loader to reduce noise induced by air flow in the drive
- New bezel and top cover design
- IDE cable Short prevention
- Isolate IDE connector and bottom cover to prevent IDE cable short caused by direct contact with bottom cover
- Disc scratch free design
- New tray design with contacting slope to prevent disc scratched by tray in OD area.
Essentially, it protects you from exploding discs (didn’t Lite-On say they weren’t really concerned about this?) and its quieter.
Improvement of LTD166S
- Tray in out noise improvement
- Improve precision of center distance and grade of gears.
- Optional dual driving type ( gears train /belt).
- Better dust proof
- No slots around screw hole on bottom cover.
- Labyrinth dust-path design on chassis.
- Flatness spec. improvement of bezel and door.
- Better ESD/EMC margin.
- Protection wall on tray motor.
- Front screw holes are closer to bezel.
- Better non-op shock and drop capability
LTD-166S : Traverse design
- Symmetric suspension points ( good for vibration).
- Light weight ( good for vibration)
- Strong structure against drop or shock