Certina 17.10-770, Mainspring

• CERTINA original mainspring in factory sealed packaging.

• Fits cal: 17.10, 17.11
  

Versions, Manual wind:

• 17.10:   18.000 A/h, manual wind, sub second.
• 17.11:   18.000 A/h, manual wind, sub second, maunting flanges on plate.
• 17.12:   19.800 A/h, manual wind
• 17.25:   19.800 A/h, manual wind, sweep second.
  
• 17.251: 19.800 A/h, manual wind, sweep second, date.