OMEGA Crowns, thread: 1.20 mm.

The Omega crown with 1.20 mm thread and 2.5 mm case tube is mainly for the manual wind 30 mm movements from the -40's to the beginning of the -60's.

Pre-Seamasters, crown number:

• 30, 30T2PC: crown without logotype.
  

• 265, 266, 283, 284: crown: 4502
  

Seamaster, Seamaster 30 crown number:

• 267, 268, 269, 285, 286: crown: 4503, 45003, 4504
  

• 269, 286: crown: 4222, 4504