Zenith Caliber 2310: A Legendary Manual-Wind Chronograph Movement

The Zenith Caliber 2310 is a manual-wind chronograph movement regarded as one of the most beautiful, reliable, and respected chronograph calibers of the 20th century. Introduced in the 1960s, this movement wasn’t just a product of Zenith—it was also produced under Martel Watch Co., a high-end movement supplier that Zenith had absorbed in the 1950s. Known for its robust column-wheel design and clean architecture, the 2310 served as the foundation for some of the most iconic chronographs in horological history.

Most famously, Omega modified this caliber into its legendary Caliber 321, used in the Speedmaster Moonwatch, which famously went to the Moon with NASA.

A Chronograph for the Ages

Zenith Caliber 2310 was developed during a time when manual-wind chronographs were the ultimate expression of mechanical complexity and precision. It featured a column wheel and horizontal clutch, the gold standard for professional chronographs, known for their crisp engagement and long-term reliability.

This movement helped establish Zenith as a key player in the chronograph market in the years before the automatic chronograph race culminated in the launch of the El Primero in 1969.

Technical Specifications

• Caliber: Zenith 2310

• Type: Manual-wind chronograph

• Jewels: 17 to 19 (varied by version)

• Frequency: 18,000 vibrations per hour (vph)

• Power Reserve: Approx. 38–40 hours

• Functions: Hours, minutes, small seconds, central chronograph seconds, 30-minute counter (often at 3 o’clock), 12-hour counter (at 6 o’clock depending on version)

The movement measures around 27 mm in diameter and just under 6 mm thick, making it compact enough for elegant chronograph cases while still offering a full three-register layout in some versions.

Its architecture is highly traditional but thoughtfully executed, with beautiful finishing, polished levers, chamfered bridges, and a blued column wheel—features often visible through casebacks in modern watches that use derivative versions of this movement.

Legacy and Influence

Though Zenith used the Caliber 2310 in several of its chronographs during the 1960s, the movement gained international fame through Omega’s version, the Caliber 321, which was based on the same Martel ébauche. Omega made minor modifications but retained the movement’s soul. The 321 powered early Speedmasters, including those certified by NASA for manned spaceflight.

That connection brought global attention to the 2310’s underlying brilliance. It’s a rare instance where a base movement achieved historic status under more than one prestigious brand.

Performance and Servicing

The 2310 is highly respected among watchmakers for its durability and serviceability. The column-wheel system, while more complex than cam-switched chronographs, allows for clean actuation and long-term mechanical stability when properly maintained.

Parts availability remains decent due to the popularity of the 321 family, and vintage specialists are well-acquainted with this architecture. When regulated properly, Cal. 2310-based watches perform with excellent accuracy for a vintage chronograph.

Collector Appeal

The Zenith 2310 is a highly collectible movement, both in original Zenith watches and in the broader context of its Martel/Omega lineage. Collectors value it for:

• Its classic column-wheel construction

• Its historical significance (as the base of the Moonwatch movement)

• Its high-quality finishing and technical elegance

Original Zenith chronographs with Cal. 2310, especially those in solid gold or steel cases with panda or tri-compax dials, are in growing demand. Rarity and condition greatly affect value, but they consistently appeal to vintage purists and chronograph enthusiasts.

Final Thoughts

The Zenith Caliber 2310 is one of the most important chronograph movements of the 20th century. With its traditional architecture, proven performance, and pivotal historical role, it bridges the worlds of fine watchmaking and scientific achievement. Whether housed in a Zenith-branded watch or recognized as the root of the Omega 321, the 2310 remains a masterpiece of manual chronograph engineering—a true icon in motion.