Reference library

Plain-language reference guides for people choosing and owning a luxury watch. Each guide below explains one topic in detail, using published figures and flagging anything that is contested, so you can check a claim before you rely on it. The guides are written to be read alongside the buying guides and articles in our journal, and they link to related pages where a topic overlaps.

• Watch Bracelet and Clasp Types: A Reference — Jubilee, Oyster, President and Pearlmaster bracelets, plus Easylink, Glidelock, Fliplock and Tudor clasp adjustment specs, with contested dates flagged.
• Case Size vs Lug-to-Lug — Diameter is what brands print, but lug-to-lug decides whether a watch overhangs your wrist. Verified model figures, measurement methods, and honest fit heuristics.
• Service Intervals by Brand: Official vs Observed — Published service intervals for Rolex, Omega, Patek, AP, Tudor and Grand Seiko, set against what watchmakers observe by movement generation.
• Water Resistance Ratings Explained: ISO 22810 vs 6425 — What ISO 22810 and ISO 6425 actually test, why a 30m rating is not a swimming depth, and why a 200m diver is pressure-tested to 250m.