"In 1989 IWC first manufactured its Ingenieur which was able to withstand huge magnetic fields of up to
500,000 A/m 
. In 1993, when IWC celebrated its 125th birthday, the company substituted this model with a more conventional Ingeneur, resisting magnetic fields of 80,000 A/m. IWC Pilots' watches demonstrate accurate time-keeping under moderate magnetic pressures as well.
New version of the MilgaussThe Rolex Milgauss series of antimagnetic certified chronometers was first manufactured in 1954 with the model 6541 for those working in nuclear, aircraft, and medical settings associated with strong magnetic fields. An aesthetically plainer model 1019 replaced the first version in the early 1960s and remained in production through 1988. Rolex reintroduced its antimagnetic Milgauss series with model 116400 in 2007 whose design invokes its 1950s predecessor and retains the line's advertised magnetic flux density resistance of 1,000 gauss within magnetic fields of 80,000 A/m." - quoted from wikipedia...