Certina 17.02-770, Mainspring

• CERTINA/ETA original mainspring in factory packaging.
  

• Fits cal: 17.02, 17.021
  

Versions with ETA base caliber:

• 17.011:  (ETA 2671) 28.800 A/h, automatic wind, sweep second, date.
  
• 17.02:    (ETA 2660) 28.800 A/h, manual wind, sweep second.
• 17.021:  (ETA 2661) 28.800 A/h, manual wind, sweep second, date.