The Timepiece Journal » watchmaking

The Geneva Seal certifies craftsmanship. COSC certifies accuracy. Learn the key differences between these two respected Swiss watch certifications.

The Geneva Seal is one of watchmaking's most respected quality hallmarks. This complete guide explains what it certifies, how it differs from COSC, and why it matters.

Authoritative answers to the most common technical questions about watchmaking — gear ratios, electrical units, magnetism, battery voltage, tolerances and fits, and heat treatment.