The FHF ST 691 is a manual-winding mechanical movement produced by Fabrique d’Horlogerie de Fontainemelon (FHF), a leading Swiss ébauche manufacturer. This caliber is part of the FHF 69 movement family, which includes a wide range of compact, two-hand calibers developed primarily for ladies' watches and elegant, slim wristwatches from the mid to late 20th century.

The “ST” prefix stands for Standard, indicating that this version was built for broad market use, offering durability, serviceability, and compatibility with various case designs.

Technical Specifications

• Type: Manual winding

• Size: 6¾ x 8 ligne (approx. 15.3 mm x 18.1 mm)

• Height: ~3.0 mm

• Jewels: 17

• Frequency: 21,600 vibrations per hour (vph)

• Power Reserve: Approximately 42 hours

• Functions: Hours and minutes (no seconds hand)

Design Features

The FHF ST 691 is a minimalistic, reliable time-only movement with:

• Two-hand configuration – no seconds for maximum simplicity and slimness

• Shock protection, typically Incabloc, enhancing durability

• A clean and efficient gear train, suitable for small watches

• A well-balanced layout allowing for easy servicing and high interchangeability with similar movements

It was optimized for cases that required compact dimensions and a low profile, often seen in vintage rectangular or oval watches.

Applications in Watchmaking

The FHF ST 691 was widely used in:

• Ladies’ dress watches, especially those made from the 1950s to 1980s

• Slim rectangular and tonneau-shaped models

• Time-only Swiss export watches

• Private-label watches designed for affordability and elegance

Its versatility and compact design made it a go-to movement for manufacturers seeking a dependable, small mechanical caliber.

Watchmaker’s Perspective

Watchmakers appreciate the FHF ST 691 for:

• Simplicity and reliability – ideal for training and repairs

• Parts compatibility within the broader FHF 69 family

• Robust construction, suitable for long-term use

• Consistent availability of spares for restoration work

The movement’s straightforward architecture allows for easy regulation, cleaning, and lubrication.

Conclusion

The FHF ST 691 is a practical, compact manual-wind movement built to meet the demands of elegant and space-efficient timepieces. Known for its reliability and ease of service, it remains a staple among vintage watch collectors and repair professionals. Whether found in a gold-plated dress watch or a discreet Swiss steel model, this caliber exemplifies the understated quality of traditional Swiss mechanical design.