Certina 13.20-770, Main spring

• Manufacturer: Prima, no: 135 D 21

• Fits cal: 13-20, 13-21

• H: 1,35
• D: 5,5
• F: 0,065
• L: 210

Versions:

• 13-20: N: = 19.800, no mountings.
• 13-21: N: = 19.800, mounting threads.
• 13-22: N: = 21.600, mounting threads.