MST 520,  521 
Ligne12''' 12'''

Remarks: This is the hacking manual version of the MST52x series - all (appropriate) parts being interchangeable accross the family. This movement was the final MST designed movement family and was developed in conjunction with Tissot and Certina (although solely a Roamer design). The movement features a large balance, beat correction, hack acting on the 4th (seconds) wheel, solid bankings and an extremely interesting click design on the ratchet wheel.
 
Production period: 1973-76

Jewels: 17
Beat: 21600
Winding: manual
Manufacturer: MST
Hand sizes:
Hour:150
Minute: 90
Second: 25
  
Stem tap size: N/A

Variant:
MST 520 12''' (26mm) direct sweep seconds
MST 521 12''' (26mm) direct sweep seconds, date

Common parts/Interchange
Balance Staff:
MST part number:7535,  interchanges with MST: 520, 521, 522, 523
Mainspring:
MST part number:1309 interchanges with MST: 520, 521, 522, 523
Strength: 0.112
Height: 1.30
Length: 380
Watches in my collection with the MST520:

All text and images are either © Kris Bubendorfer 2011-15 or © Roamer Watch Company.