Movement record · Switzerland

ETA/Unitas 6497

Partially verified

A large, simple bridge-type hand-wound calibre originally supplied as a pocket-watch movement and later widely re-used, undecorated or finished to order, in mechanical wristwatches valued for their visible, easily serviced construction.

Technical specifications

Diameter: 36.6 mm (16½ lignes)
Height: Approx. 4.5 mm
Jewels: 17 (base); higher-jewel and decorated versions exist
Frequency: 18,000 vph (2.5 Hz), later variants at 28,800 vph
Power reserve: Approx. 46 hours
Winding: Hand wind
Setting: Pull-out crown, sweep or small seconds depending on variant
Escapement: Swiss lever
Balance: Glucydur-type balance with Nivarox hairspring on later production
Complications: Subsidiary seconds (6497); centre seconds on the related 6498 layout varies by source

Identification features

Large 36.6 mm plate size unusual in a wristwatch
ETA or Unitas signature on the bridge of unbranded examples

Known variants

6497-1 (small seconds)
6498-1 (centre seconds arrangement)

Servicing notes

Straightforward to service given its size and simple bridge layout; parts remain widely available.

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

Historical significance

A late-surviving pocket-watch calibre that became, from the early 2000s, one of the most widely used base movements in revival mechanical wristwatches.

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

ETA technical documentation
Trade literature on base-calibre re-use

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