Longines Caliber 380 – An Early Electro-Mechanical Chronograph Movement

The Longines Caliber 380, also known as the Caliber 6312, is a rare and technically significant electro-mechanical chronograph movement developed in the early 1970s. It stands at the intersection of traditional mechanical watchmaking and the emerging electronic technology that eventually dominated the watch industry during the quartz revolution.

Introduced during a time of innovation and transition, the 380 represents Longines' attempt to modernize the chronograph by integrating electronic timekeeping with mechanical chronograph operation, making it one of the few hybrid movements of its time.

Technical Specifications

Key Features

• Balance wheel with electronic impulse: Unlike modern quartz movements with stepper motors, the 380 uses a traditional balance wheel regulated by an electromagnetic circuit, similar to ESA Dynotron systems.

• Mechanical chronograph: Despite being electronically regulated, the chronograph mechanism is fully mechanical, featuring a central chronograph seconds hand and a 30-minute totalizer.

• Crown and pusher layout: The movement operates like a classic chronograph, with start/stop/reset pushers typically placed at 2 and 4 o’clock.

• Date-free layout: Most versions of the 380 are time-and-chronograph only, keeping the dial clean and symmetrical.

Historical Importance

• The 380 is part of Longines’ transitional era, between purely mechanical calibers and full quartz modules.

• It was released alongside other experimental electro-mechanical movements and was used in select chronograph models aimed at professionals—especially in aviation or timing sports events.

• Its rarity today reflects both its limited production run and the industry-wide shift toward quartz in the mid-1970s, which quickly rendered such hybrid calibers obsolete.

Applications and Models

Watches housing the 380 were generally:

• Medium to large-sized chronographs (typically 36–38 mm)

• Offered with sporty dials—tachymeters, contrasting subdials, and luminous hands

• Cased in stainless steel with screw-down or snap case backs

• Produced in low volumes primarily for markets interested in precision timing tools

These watches are now considered collectible and historically relevant, especially in the context of pre-quartz chronograph development.

Servicing Considerations

The 380 is serviceable, but it presents unique challenges:

• Spare parts are scarce, especially for the electronic coil, circuit board, and balance module.

• Battery compatibility must be considered carefully—original mercury batteries are no longer available, so modern alternatives like zinc-air or silver oxide may be used with voltage correction.

• Chronograph module must be treated like a mechanical caliber, with proper cleaning, lubrication, and adjustment.

Only watchmakers experienced in vintage electro-mechanical movements should attempt full service or restoration.

Conclusion

The Longines Caliber 380 is a fascinating and technically bold movement from the dawn of electronic watchmaking. Blending mechanical chronograph heritage with electromagnetic regulation, it stands as a transitional piece of horological history. Though short-lived in production, the 380 remains a rare collector’s item, valued for its innovation, craftsmanship, and role in bridging two great eras of watch technology.