Watch family · Precision & certification
Antimagnetic Watches
Partially verifiedWatches constructed or shielded so that magnetic fields do not affect the rate of the balance and hairspring, addressing a timekeeping fault first identified and remedied in pocket watches.
Movement & mechanism
- Balance, hairspring and escapement components made from, or coated with, non-ferrous or weakly magnetic alloys
- In some designs, a soft-iron inner case forming a Faraday-cage-like shield around the movement rather than relying solely on component materials
- Rate testing before and after exposure to a magnetic field to verify antimagnetic performance
Identification
- Case back or dial marked 'antimagnetic' or with a specific antimagnetic standard reference
- Soft-iron inner cap visible if the case is opened, in shielded-case designs
Terminology
- Antimagnetic alloy — a balance or hairspring material chosen for low sensitivity to magnetic fields
- Soft-iron cage — an inner case shield used to protect the movement from external magnetic fields
Known variations
- Antimagnetic balance/hairspring alloy without shielding
- Soft-iron shielded case
- Combined alloy and shielding construction
Pocket-watch ancestry
Antimagnetic balance and hairspring alloys were developed and patented for pocket watches in the later nineteenth century in response to growing use of electrical and magnetic equipment; wristwatch makers adopted the same materials and, later, the shielded-case principle once magnetic exposure (from electrical appliances, generators and similar sources) became a recognised hazard to wrist-worn movements as well.
Collecting notes
A precision and certification category collected alongside chronometer and railway-grade watches, with genuine documented antimagnetic testing of particular interest to specialists.
Background
Antimagnetic watches are designed to maintain accuracy when exposed to specific levels of magnetic fields, addressing a challenge in mechanical timekeeping. The first antimagnetic wristwatch was produced by Tissot in 1930. Watchmakers utilize two primary methods to achieve resistance: employing non-magnetic alloys for movement components or housing the movement within a highly permeable soft-iron case.
Common alloys developed for these timepieces include Invar, Glucydur, Nivarox, and Elinvar, which serve to minimize magnetic influence on the hairspring and balance. International standards like ISO 764 govern the testing of these watches, requiring them to resist exposure to a direct current magnetic field of 4800 A/m.
Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.
Defining features
- Where the movement is housed in a magnetically conductive case, an additional soft-iron cover over the movement stops magnetic fields forming inside the watch.
- Certification standards like METAS N001 require movements to withstand magnetic fields of 1.5 tesla without significant deviation.
Later development
- Rolex introduced the Milgauss series in 1954 to serve professionals in nuclear, aircraft, and medical settings.
- IWC released the Ingenieur Reference 3508 in 1989, capable of withstanding magnetic fields up to 500,000 A/m.
- Omega announced a movement in 2013 that avoids protective containers in favor of non-ferrous materials to resist 1.5 tesla.
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- Antimagnetic watch, Wikipedia (English), retrieved 2026-10-28 (text CC BY-SA 4.0)
- General literature on antimagnetic balance and hairspring materials in pocket- and wristwatch history; individual patent priority requires further research.
Where sources disagree, the disagreement is stated rather than resolved silently.