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Brand: | Landeron | 
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|---|---|---|---|
| Family: | |||
| Height: | 7.42 mm | ||
| Jewels: | 17 | ||
| Reserve: | hours | ||
| Frequency: | 18,000 A/h | ||
| Winding: | Hand winding | ||
| Diameter: | 31 mm (13.75 ligne) | ||
| Complications: | 2-Button, Cam Switching Chronograph, Chronograph, Date, Date by Pointer, Day, Horizontal Clutch Chronograph, Month, Moon Phase | ||
| Hands: | 30 Minute Chronograph Hand at 3:00, Central 60 Second Chronograph Hand, Central Date Pointer, Central Hour Hand, Central Minute Hand, Day Window at 11:30, Month Window at 12:30, Moon Phase Wheel at 6:00, Small Seconds Hand at 9:00 | ||
| Distinguishing Technical Characteristics | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
 Hand-Winding  Clockwise Balance Cock  Screwed Balance  Indexed Regulator |
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| Production: – | |||||||||||
| 1910s | 1920s | 1930s | 1940s | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
Cal. 81 is a cam-switching chronograph movement with full calendar and moon phase produced by Landeron (Charles Hahn & Cie.) Based on the simple Cal. 51 and full calendar Cal. 80, Cal. 81 was the first of Landeron’s mainstream Cal. 48 family to feature a moon phase complication. Cal. 81 is very similar to the later Cal. 181.
Most of the Cal. 48 movements feature a date pointer at 6:00, but this dial position was taken by the moon phase indicator. Rather than having a co-axial date subdial, Cal. 81 and variants use a central date pointer, the only such indication in this family of movements.
The date complication is adjusted using pushers inset into the case:
- 2:30 – Month
- 8:00 – Moon phase
- 9:00 – Date pointer
- 10:00 – Day
