ISO 764:2020, Horology — Magnetic resistant watches, states: "This document specifies the minimum requirements and test methods for magnetic resistant watches. This document applies to magnetic resistant watches designed to withstand daily magnetic fields. Moreover, it indicates the marking which the manufacturer is authorized to apply to them."
The phrase "daily magnetic fields" is the boundary of the standard. High-field claims (METAS certifies resistance to 1.5 T, or 15,000 gauss) are a different and much more demanding thing, and are not what an ISO 764 marking indicates.
Edition 4, published February 2020, confirmed as an International Standard.
Sources
Every statement above traces to one of these. Read on the date shown.
- Tier 1 ISO 764:2020, Horology — Magnetic resistant watches, edition 4, published February 2020, source read 2026-09-26