Longines Caliber 431 – A High-Beat Chronometer Movement with Technical Refinement

The Longines Caliber 431 is a manual-winding mechanical movement, introduced in the late 1960s as an evolution of the brand’s high-frequency 400 series. Closely related to Caliber 430, the 431 was developed with a clear focus on chronometric precision, durability, and slim design, making it a flagship manual caliber for Longines during the transitional period before quartz technology took over the market.

What sets the 431 apart is its COSC-certified chronometer status, making it one of Longines’ most accurate in-house hand-wound movements of the era.

Technical Specifications

• Type: Manual-winding chronometer-grade movement

• Base Caliber: Longines 430

• Diameter: Approx. 23.3 mm

• Height: Around 3.6 mm

• Frequency: 36,000 vibrations per hour (5 Hz)

• Jewels: 17

• Power Reserve: Approximately 42 hours

• Functions:

  • Hours

  • Minutes

  • Central seconds

High-Beat Performance

Caliber 431 operates at 36,000 vibrations per hour, or 5 Hz, a frequency associated with superior rate stability and a smoother sweep of the seconds hand. This movement was Longines’ response to the increasing demand for high-precision chronometers, particularly during the 1960s race to develop ultra-accurate mechanical wristwatches.

This frequency places the 431 among other elite high-beat movements of the time, such as Zenith’s El Primero and Girard-Perregaux's HF chronometers. The higher beat rate improves isochronism, better resisting timing variation caused by changes in position or power reserve.

Chronometer Certification

The 431 was frequently submitted for COSC testing, and many watches featuring this movement are marked as officially certified chronometers. To meet the chronometer standards, Longines ensured each movement was finely adjusted in multiple positions and temperatures, with careful regulation of the balance and hairspring.

This makes the Caliber 431 not only technically advanced but also historically important as a symbol of Longines’ commitment to precision watchmaking.

Construction and Finishing

Structurally, the 431 shares much of its architecture with Caliber 430 but features enhanced finishing, improved components, and refined regulation systems to handle the high-frequency operation. Key features include:

• A precisely engineered balance wheel and hairspring, optimized for 5 Hz operation

• Hardened gear train pivots to reduce friction and wear

• A manual winding mechanism that operates smoothly, with durable ratchet and crown wheels

• Slim profile suitable for thin, dress-oriented chronometer cases

Decoration ranged from utilitarian in steel-case models to more refined finishing in gold versions. Regardless of aesthetics, the mechanical quality remained consistently high.

Applications and Watch Models

Longines used the Caliber 431 in several of its Flagship and Ultra-Chron models, particularly those aimed at professionals and enthusiasts demanding certified accuracy. These watches often bore the Ultra-Chron logo on the dial and sometimes on the case back.

Cased in gold, gold-cap, or stainless steel, the watches housing Cal. 431 were usually sleek and understated, with thin profiles, baton markers, and clean dials. Case sizes typically ranged from 34 to 36 mm.

Servicing and Longevity

Like all high-frequency movements, the Caliber 431 requires expert handling during servicing. Its fast-beating escapement puts more stress on the lubricated surfaces, so regular maintenance is more critical than on slower movements.

Original parts are increasingly rare, especially for the balance assembly and escapement. However, when properly maintained, the 431 is a very stable and accurate movement, a testament to Longines’ engineering excellence.

Conclusion

The Longines Caliber 431 represents one of the most advanced manual-winding movements ever produced by the brand. With its high-beat 36,000 vph operation, chronometer certification, and slim design, it embodies the final achievements of traditional mechanical watchmaking before the quartz revolution. For collectors and horology enthusiasts, the 431 is a remarkable example of Longines' innovation, precision, and commitment to excellence in the golden age of mechanical timekeeping.