The movement of a mechanical or quartz watch can be disrupted if it comes near a strong magnetic field. Magnetism is common in a wide variety of electronic products, automobiles, and kitchen utilities, such as refrigerators.
Many Swiss watches claim to be anti-magnetic, which is achieved by using a protective case and alloys for certain parts, such as the balance wheel and escape wheel. These include Invar (iron, nickel, carbon, chromium alloy), Glucydur (beryllium, bronze alloy), and Nivarox (iron, nickel, chromium, titanium).
In early 2013, Omega announced it had created a variant of the Omega Seamaster Aqua Terra (pictured above) that is resistant to magnetic fields greater than 1.5 tesla (15,000 gauss), far exceeding the levels of magnetic resistance achieved by any previous watch ever made.
What makes the co-axial calibre 8508 unique is the the use of selected non-ferrous materials in the movement itself without the use of a protective case. This allows the movement to be viewed through a see-through display back.