The Tissot caliber 27B-1 is a manual-winding mechanical movement from the 1940s and 1950s, part of Tissot’s well-established 27-series of in-house calibers. This series represents one of the brand’s most enduring and reliable families of movements, used across a wide range of classic, time-only wristwatches during the mid-20th century. The 27B-1 is a variation of the base caliber 27B, tailored for specific case or dial configurations while maintaining the series' mechanical integrity.

Overview of the Caliber 27B-1

The 27B-1 was developed for simple, elegant wristwatches with a focus on accuracy, slimness, and reliability. Watches powered by this movement were typically:

• Manual-wind

• Featuring hours, minutes, and a small seconds subdial at 6 o'clock

• Cased in steel or gold-plated cases, often sized between 32 mm and 36 mm

• Designed with minimalist, legible dials that reflect the aesthetic of the post-war era

The “-1” suffix indicates a minor technical evolution or adjustment to the original 27B, such as modified bridge shape, setting mechanism changes, or dial foot placement to suit different models.

Technical Specifications

• Type: Manual winding

• Functions: Hours, minutes, small seconds

• Jewels: 15

• Frequency: 18,000 vibrations per hour (2.5 Hz)

• Power Reserve: Around 40 hours

• Diameter: Approximately 27 mm (12 lignes)

• Height: ~4.0 mm

• Shock Protection: Some versions include basic protection like Incabloc; early examples may have none

• Finishing: Matte or brushed plates, blued screws, and stamped Tissot bridge

Built with a Swiss lever escapement, the 27B-1 is designed for accuracy, simplicity, and long-term serviceability.

Service and Maintenance Guidelines

Like all vintage mechanical movements, the Tissot 27B-1 requires regular servicing to ensure longevity and reliability. A full overhaul is recommended every 4 to 6 years, even if the watch appears to be running.

A proper service includes:

1. Disassembly of the entire movement

2. Ultrasonic cleaning of all parts

3. Inspection and replacement of worn components (e.g., mainspring, crown, pivots)

4. Lubrication with modern synthetic oils

5. Reassembly and regulation in multiple positions

6. Cleaning of the case and possible replacement of gaskets (if applicable)

Servicing should be done by a watchmaker experienced with vintage Swiss mechanical calibers, as parts may need to be sourced from donor movements.

Common Points of Wear

• Mainspring barrel and arbor – often fatigued due to age

• Balance pivots and cap jewels – prone to wear if run dry

• Keyless works (winding and setting parts) – can loosen over time

• Small seconds wheel – constant rotation can lead to gear wear

• Crown and stem – may become loose or corroded

Handling Tips

• Wind the watch once daily, stopping as soon as you feel resistance

• Avoid exposure to moisture or water, especially if the case has not been resealed

• Keep away from magnets, which can disrupt timekeeping

• Store in a dry, stable environment, ideally dial-up to reduce pressure on internal components

Collectibility and Value

The Tissot 27B-1 is not considered rare, but it is well-regarded among vintage enthusiasts for its:

• Mechanical reliability

• Historical significance in Tissot’s mid-century production

• Classic aesthetic, ideal for vintage dress watches

• Ease of servicing and availability of donor parts

It remains an affordable and accessible entry point into vintage Swiss mechanical watch collecting.

Conclusion

The Tissot caliber 27B-1 is a durable, well-designed vintage movement that powered many of Tissot’s elegant wristwatches during the mid-20th century. With its smooth winding, steady timekeeping, and serviceable architecture, it stands as a testament to Tissot’s craftsmanship in an era of mechanical precision. With regular care and attention, it continues to offer reliable performance and timeless appeal.