Certina Caliber 15-21: A Trusted Manual-Wind Movement With Improved Precision

The Certina 15-21 is a manual-wind movement that evolved from the earlier Caliber 15-20. Introduced during the 1950s, the 15-21 is part of Certina’s reliable 15-ligne family. It features several refinements in finishing and mechanical efficiency, aimed at improving timekeeping consistency and ease of maintenance.

While retaining the traditional sub-seconds display and hand-wound functionality, the 15-21 introduced improved shock resistance and gear tolerances, making it a go-to caliber for Certina’s mid-century watches. It was widely used in men’s wristwatches of that period and is still appreciated today for its durability, simplicity, and serviceability.

Technical Specifications

The 15-ligne size was ideal for medium-to-large wristwatch cases, giving the movement both stability and space for effective lubrication and service access.

Mechanical Construction and Features

Certina’s 15-21 was designed with a Swiss lever escapement and a full bridge or three-quarter plate layout, ensuring excellent support for the gear train and simplifying servicing. Improvements over its predecessor (15-20) include:

• Enhanced Incabloc shock protection

• Tighter machining tolerances for improved amplitude

• Refined balance assembly for better positional accuracy

• Updated finish and part polish, reflecting higher production standards

Its manual-wind gear system is reliable and efficient, delivering consistent torque across the power reserve curve.

Applications in Certina Watches

The Caliber 15-21 was fitted in a wide range of Certina men’s wristwatches from the 1950s into the early 1960s. These watches often featured:

• Case sizes from 34 mm to 36 mm, typical of the era

• Stainless steel, chrome-plated brass, or gold-filled cases

• Sub-seconds dial layout at 6 o’clock

• Dials marked “Certina” or transitional branding from “Grana”

• Snap-on or screw-down casebacks, depending on model

The aesthetic was clean, utilitarian, and dependable—ideal for both everyday wear and office attire.

Watchmaker Notes and Service Tips

The 15-21 is known for its straightforward service profile and long-term reliability. Many vintage watchmakers consider it a good movement for both beginners and professionals due to its open bridge design and strong architecture.

Key tips for servicing:

• Use Moebius 9010 oil for the gear train and escapement pivots

• Lubricate the barrel arbor and mainspring with suitable grease

• Inspect balance staff ends and Incabloc springs for wear

• Replace the mainspring if amplitude is poor; use matched vintage-grade replacements when possible

• Regulate carefully, as balance inertia is well-tuned to respond to fine adjustments

With proper cleaning and regulation, the 15-21 can achieve ±10–15 seconds/day accuracy, which was excellent for its time.

Collector and Historical Appeal

Collectors value the 15-21 not only for its mechanical reliability but also for its place in Certina’s transitional phase between earlier hand-wind calibers and the upcoming automatic generations. It offers:

• Authentic vintage Swiss movement design

• Easy part sourcing via movement donors

• Strong service track record

• Affordability compared to rarer chronometer-grade calibers

Its widespread use makes it common but respected, especially when housed in all-original Certina cases with clean dials.

Conclusion

The Certina Caliber 15-21 reflects a period when Swiss watchmaking was focused on engineering precision, reliability, and consistency. A refinement of the 15-20, this movement brought higher accuracy and better protection into Certina’s manual-wind lineup. Whether you’re restoring a mid-century watch or seeking a reliable vintage movement, the 15-21 remains a solid choice—simple, durable, and built to last.