Movement record · Switzerland

Zenith 135

Partially verified

Manual calibre designed around an unusually large balance

Technical specifications

Diameter: Approx. 27 mm
Height: Not recorded in the sources consulted
Jewels: 18 (observatory versions differ)
Frequency: 18,000 vph (2.5 Hz)
Power reserve: Approx. 40 hours
Winding: Manual, stem wind
Setting: Pendant set
Escapement: Swiss lever
Balance: Large balance with alloy hairspring
Complications: Subsidiary seconds

Identification features

Off-centre layout giving room for a large balance
Observatory versions differ from series production

Known variants

Series production version
Observatory chronometer versions

Servicing notes

Cleaning, lubrication, mainspring and pivot work belong with a qualified watchmaker working from calibre-specific documentation. Conserve original parts: replacing a worn component with a modern substitute changes the object, and refinishing plates or dials destroys evidence.

General guidance only. Antique movements should be serviced by a qualified watchmaker.

Historical significance

A celebrated chronometry calibre: its layout was dictated by the decision to give the balance as much diameter as possible.

Diagram

Schematic: plate and bridge layout. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Sources & references

de Carle, D., Watch and Clock Encyclopedia
Period trade material catalogues and calibre reference compilations (edition-dependent)
Published manufacturer technical documentation where available

Where sources disagree, the disagreement is stated rather than resolved silently.