Omega Chronograph Pre-Speedmaster CK2077 with Caliber 33.3 from 1944

The Omega Calibre 33.3 CHRO is one of the most historically important chronograph movements ever produced by Omega and is widely regarded as the direct ancestor of the legendary Calibre 321 that would later power the first Speedmasters. Introduced in 1933 and developed from a Lemania chronograph architecture following Omega's acquisition of Lemania through SSIH, the Calibre 33.3 marked the beginning of Omega's in-house chronograph tradition and established the technical foundation for some of the most celebrated chronographs of the twentieth century.

Its designation derives simply from its diameter—33.3mm—which made it one of the largest wristwatch chronograph movements of its era. The generous dimensions allowed for an exceptionally balanced layout with oversized bridges, a large balance wheel, and robust chronograph components, resulting in a movement renowned for both its reliability and ease of servicing.

The movement is a manually wound, column-wheel chronograph featuring a horizontal clutch. Beautifully finished with Geneva stripes, polished steel components, and carefully beveled bridges, the Calibre 33.3 reflects the level of craftsmanship that defined Swiss chronograph manufacturing before the Second World War.

The first watch to house the movement was the Omega CK 2048, introduced in 1937, followed by a small number of highly collectible references including the CK 2077, CK 987, CK 988, and CK 2092. Production continued for nearly two decades before the movement gradually evolved into the Calibre 321 during the late 1940s and 1950s.

The Omega CK 2077 is widely regarded as one of the finest pre-Speedmaster chronographs ever produced. Introduced in 1937, it was Omega's first water-resistant chronograph, combining the groundbreaking Calibre 33.3 with a large screw-back case that was decades ahead of its time. 

Measuring approximately 38mm in diameter, the CK 2077 was considered exceptionally large during the late 1930s and 1940s, when most wristwatches measured between 30 and 34mm. Its broad bezel, stepped case profile, oversized pushers, and generous dial opening gave it a purposeful appearance that feels surprisingly modern even by today's standards. The screw-down caseback provided improved protection against moisture and dust, making the CK 2077 Omega's first truly robust chronograph wristwatch.

Brand: Omega
Model:  Pre-Speedmaster
Year of manufacture: 1944
Serial number: 10.389.5xx
Material: Stainless Steel
Dimensions: 38mm
Glass material: plexiglass
Reference number:  CK2077 
Movement type: Caliber 33.3 Manual winding
Bracelet: molequin leather strap
Mechanical performance warranty: 6 months
Box and documentation:  N/A

Observations: The watch works correctly, movement is currently being serviced 15/07/26