The Tissot caliber 27B-21 is a manual-winding mechanical movement and part of the highly regarded Tissot 27-series, which formed the backbone of the brand’s mechanical watch offerings from the 1940s through the 1960s. The 27B-21 is a variant of the 27B, tailored for specific case configurations, dial layouts, or manufacturing improvements. Like other 27-series movements, it was built for reliability, ease of service, and long-term durability, making it a strong representative of mid-century Swiss watchmaking.

Overview of the Caliber 27B-21

This movement was commonly found in Tissot dress and everyday watches, often featuring:

• Manual winding operation

• Central hour and minute hands

• A small seconds subdial at the 6 o’clock position

Watches using the 27B-21 were housed in modestly sized steel or gold-plated cases, typically ranging from 32 mm to 36 mm in diameter. These models followed the aesthetic of the era: simple, legible dials with either baton or Arabic numeral hour markers.

The "-21" suffix identifies this as a specific variation within the 27B family, likely reflecting differences in bridge layout, keyless works, or compatibility with different dial or casing setups.

Technical Specifications

• Type: Manual winding

• Functions: Hours, minutes, small seconds

• Jewels: 15

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

• Power Reserve: Approximately 40 hours

• Diameter: ~27 mm (about 12 lignes)

• Height: ~4 mm

• Shock Protection: May be present in later versions (e.g., Incabloc); early models typically lacked it

• Finish: Clean industrial design with matte or brushed plates, blued screws, and Tissot-stamped bridges

The movement uses a Swiss lever escapement and was engineered with practical servicing and long-term use in mind.

Service and Maintenance

As a vintage mechanical movement, the 27B-21 requires regular maintenance to keep it operating correctly. A full overhaul is recommended every 4 to 6 years, or earlier if the watch shows signs of performance issues.

A complete service includes:

1. Disassembly of all movement components

2. Ultrasonic cleaning of plates, gears, and springs

3. Visual inspection of pivots, jewels, wheels, and springs for wear

4. Replacement of worn parts such as mainsprings or balance components (sourced from donor movements if necessary)

5. Re-lubrication using modern synthetic oils

6. Reassembly and regulation for accurate timekeeping

7. Cleaning and resealing the case, if applicable

Common Wear Areas

Due to age and prolonged use, some areas may require special attention:

• Mainspring barrel—can weaken over time, affecting power delivery

• Balance pivots—may show signs of wear if lubrication has dried

• Small seconds gear—constant engagement can lead to wear or play

• Stem and crown—can become worn or loose, affecting winding or setting

• Case corrosion—especially if the watch was exposed to moisture over the years

Usage and Handling Tips

• Wind the watch daily, but stop as soon as resistance is felt

• Avoid water and humidity—most watches with this movement were not water-resistant

• Keep away from strong magnets, which can disturb the balance spring and accuracy

• Store in a clean, dry environment, preferably face-up to minimize pressure on moving parts

Collectibility and Appeal

While not rare or highly decorated, the Tissot 27B-21 is valued among enthusiasts for:

• Its historical significance in post-war Swiss watchmaking

• Reliable construction and smooth operation

• Classic design, often found in watches with strong mid-century styling

• Affordable entry point into vintage Swiss mechanical watches

These movements are commonly seen in well-preserved Tissot models that continue to offer charm and usability today.

Conclusion

The Tissot caliber 27B-21 is a dependable, no-nonsense manual-wind movement that reflects the solid mechanical principles of mid-20th-century watchmaking. It remains a great choice for vintage collectors or daily wearers looking for a watch with authentic Swiss heritage, mechanical charm, and timeless design. With proper care and regular servicing, the 27B-21 can continue ticking accurately for many more decades.