Certina 13.20-770, Mainspring
- CERTINA original part in factory packaging.
- Fits cal: 13-20, 13-21
Versions:
- 13-20: 19.800 A/h.
- 13-21: 19.800 A/h, threads for case clamps.
- 13-22: 21.600 A/h, threads for case clamps.
Versions:
