Omega Caliber 1538A: Automatic Chronograph Movement with Classic Swiss Engineering

The Omega Caliber 1538A is an automatic mechanical chronograph movement introduced in the 1970s. It builds upon the strong foundations of the 1500-series but adds chronograph complications, making it a highly versatile and precise movement favored by enthusiasts and collectors alike.

Based on the ETA/Valjoux 7750 platform, the 1538A was customized by Omega to deliver reliable chronograph functionality combined with automatic winding and a date feature.

Technical Specifications

• Type: Automatic mechanical chronograph

• Functions: Hours, minutes, central chronograph seconds, 30-minute and 12-hour counters, date, small seconds

• Jewels: 25

• Frequency: 28,800 vibrations per hour (vph)

• Power Reserve: Approximately 44 hours

• Hacking Seconds: Yes

• Diameter: Approximately 30 mm

• Thickness: Around 7.9 mm

Watches Featuring Caliber 1538A

The Caliber 1538A was used in:

• Omega Speedmaster Mark series chronographs from the 1970s

• Other limited edition or special Omega chronograph models

• Watches requiring a robust automatic chronograph with added date function

These watches typically feature:

• Stainless steel or gold-plated cases

• Chronograph subdials at 3, 6, and 9 o’clock

• Date windows positioned between 4 and 5 o’clock

• Sapphire or acrylic crystals depending on the model and production year

Performance and Durability

The 1538A movement is renowned for:

• Smooth automatic winding with reliable chronograph operation

• Precision timing of events via central seconds and subdials

• Quickset date function for easy calendar management

• Hacking seconds to enable precise time synchronization

Its 28,800 vph beat rate provides a balance of accuracy and durability.

Maintenance and Servicing

The 1538A requires:

• Regular servicing every 4–6 years, especially important due to chronograph complexity

• Cleaning and lubrication of mechanical components

• Inspection and potential replacement of worn parts, including chronograph mechanisms

Parts and servicing expertise are widely available due to its common ETA/Valjoux base.

Collector Appeal

Collectors highly value the Omega Caliber 1538A for:

• Its blend of automatic chronograph functionality with classic Swiss engineering

• Its presence in collectible Speedmaster and other chronograph models

• High reliability combined with mechanical sophistication

• Its suitability for vintage restoration and maintenance

Final Thoughts

The Omega Caliber 1538A stands as a testament to Omega’s mastery in producing automatic chronographs that balance precision, durability, and functionality. It remains a sought-after movement for collectors and enthusiasts of vintage mechanical chronographs.