The Rolex Oyster Perpetual Milgauss is a wristwatch model introduced by Rolex in 1956 with model number 6541. The Milgauss was designed as an antimagnetic watch specifically for those who worked in power plants, medical facilities and research labs (like those in Geneva[examples needed]) where electromagnetic fields can cause havoc with the timing of a watch. The current[when?] model Milgauss is equipped with amagnetic alloy (Parachrom-Blu) hairspring and movement encased by a magnetic shield (note: this is not a Faraday cage, which only shields electrostatic fields), most likely[vague] composed of a high magnetic permeability material (see Mu-metal or Permalloy). The name Milgauss is derived from the Latin mille, which means one-thousand, and gauss, the unit of a magnetic field. This model is so named because it can withstand a magnetic flux density of 1,000 gauss.
The original Milgauss was very similar to the appearance of the Rolex Submariner, with an oversized case and bezel, with the Twinlock crown, and a riveted Oyster bracelet. Although the Milgauss only went through two different models (6541, 1019) the Milgauss went through numerous configuration changes before being discontinued in 1988.
The Milgauss remains a sought after model amongst Rolex collectors due to its relatively low sales and popularity during the 1960s and 70s, it has become rare in today's vintage watch market. A vintage Milgauss signed by Tiffany & Co. recently sold for over $32,000.
In 2007, Rolex brought back the Milgauss after nearly two decades as the model number 116400. There are currently four versions: white dial or black dial with a standard colorless sapphire crystal and the GV (Glace Verte) with black or blue dials. Rolex presented the new version with electric blue dial and green-tinted sapphire glass in 2014.  The GV is the only Rolex produced with a tinted crystal. Although initially rumored to be a limited edition, the GV version is still produced nearly 3 years later.
Due to its internal magnetic shield, the Milgauss is thicker than the Submariner, but the same width and weighs 157 grams. The Milgauss is only available in 904L polished stainless steel, an alloy that is extremely resistant to scratches and corrosion. Aside from its resistance to magnetic fields, the Milgauss' most unusual feature is its orange lightning-bolt second hand, a unique feature in the Rolex lineup that was originally introduced with the 6541 Milgauss model.
In 2008, the MSRP for it was $6,200 and selling at or below retail. The MSRP for the GV was $6,575 and it was selling above retail in most situations. A short time before its release, resellers and retailers were asking as much as double retail in anticipation of the new model.
- The Rolex Report pg. 60 by John E. Brozek