Magnetic fields can affect a watch’s accuracy by influencing the oscillation rate of the balance. Attempts to overcome this problem started in the mid 19th century by Vacheron Constantin. They eventually produced the first non-magnetic pocket watch in 1915, following the development of nickel based alloys which also ensured watches were less affected by temperature variation. Tissot produced the first anti-magnetic watch in 1929. A watch must maintain its accuracy to +/- 15 seconds per day when exposed to a magnetic field of 4500 amperes to meet the international standards.