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