Rolex introduced a number of tool watches in the 1950s, including the Explorer and Submariner. The first anti-magnetic Milgauss model, Ref. 6451, first appeared in 1954 alongside the similar Submariner model. It featured an anti-magnetic movement with soft iron dial and rear disc inside the Submariner case. The name derived from the French, mille Gauss, indicating resistance to magnetic fields over 1,000 Gauss.
A lightning bolt-shaped seconds hand is the most recognizable feature of the model, but this is not present on many classic examples. Most have a honeycomb dial with arrow-shaped markers at 3, 6, and 9, dots at the other hours, and dauphine hands. But Milgauss was really just a feature added to the Oyster Perpetual line, so variations abound.
The original Milgauss reference was updated in 1957 with a new Ref. 1019 with either a white or black dial. Although early versions of this reference lack the lightning bolt seconds hand, but later versions may have included it. Many were fitted after the fact with this distinctive element. The Milgauss was discontinued in 1988.
In 2007, Rolex reintroduced the Milgauss model at Baselworld. The new Ref. 116400 again features a soft iron inner case but it is the new Cal. 3131 that offers the most protection. It includes the Parachrom Blu hairspring and a pallet fork and escape wheel made of non-magnetic amorphous nickel-phosphorous. The Milgauss lacks a date window or display caseback (like most Rolex models) to further protect the movement. The new 40 mm case (including the anti-magnetic components) is shared with the updated 2016 Air-King Ref. 116900.
The new Milgauss sports the orange lightning bolt seconds hand of the original with a distinctive dial with all-rectangular markers. A “Glace Verte” (“GV”) version with a green-tinted sapphire crystal was intended to be a special 50th anniversary homage but remains available as of 2018. A blue-dial and green glass, the “Z Blue” was introduced in 2014 and clear-crystal versions retired shortly after.