Overview
ISO 3160-1:1998 - Watch-cases and accessories - Gold alloy coverings - Part 1: General requirements defines general requirements for gold-alloy coverings applied to watch cases and their accessories, including bracelets. It sets definitions, minimum gold content, nominal coating thicknesses, marking rules and references to test and measurement methods. This standard is essential for consistent quality, consumer information and regulatory compliance in horology and metal finishing.
Key topics and requirements
- Scope: Applies to watch-cases, bracelets and related accessories receiving gold-alloy coverings.
- Definitions: Distinguishes plaqué or (gold plated), plaqué or laminé (gold-clad/rolled gold) and coiffe or (gold cap). Also defines surface significative (surface essential to appearance/function) and titre (gold fineness in millièmes).
- Minimum gold content: The alloy fineness (titre) for all covering types must be at least 585 millièmes (commonly referred to as 14 carat).
- Nominal coating thicknesses (with ±20% tolerance):
- Plated gold (GP) and rolled gold (GR): 5, 10, 20, 40, 80 µm
- Gold cap (GC / coiffe or): 200, 250, 300 µm
- Measurement and testing:
- Thickness measurement and fineness determination are to follow methods given in ISO 3160-2.
- Abrasion and wear tests are specified in ISO 3160-3.
- Marking rules:
- Marks must include type letters (GP, GR, GC), nominal thickness in µm and a maker’s or responsibility punch.
- Example marks: GP 10, GR 20, GC 250.
- Marking is mandatory for coverings ≥ 5 µm, forbidden for coatings
