Master of G
The Master of G series is a collection of G-Shock watches produced by Japanese electronics and wristwatch manufacturer Casio in the late 1990s. There were several models in the range, as these were designed for use in harsh environments, and many were designed to showcase a new form of technology that Casio would eventually introduce into the G-Shock and ProTrek outdoor ranges, such as the Tough Solar power source, altimeter function and digital compass.
The Master of G series began in 1985 with the G-Shock II, model number DW-5500C. This was a classic square G-Shock, but the bezel contained softer parts and slipped over the buttons. This way Casio created a Mud Resistant structure. The DW-5500C was therefore nicknamed "Mudman". It took until November, 1993, before Casio came up with the Frogman model, however at this stage the watch was not called a Frogman, except in Japan where the case-back did feature the word "FROGMAN" and a small figure of a diving frog. The Frogman was a heavy divers model that featured a unique asymmetrical design of thick rubber shielding around a self-contained module, with titanium screw-back case—an unusually high-cost design. A thick double-tang resin strap and multitude of digital features including dive timing completed a competent diver's watch. The Frogman proved to be very popular, and this is presumably one of the key reasons why at some point between then and 1995 Casio decided to produce more high-end premium models, and with them limited edition colour variants that, due to their scarcity, have in some cases become very valuable indeed.
It seems that the last of the "first wave" of Masters watches ceased production around 2000, but there are signs Casio is keen to keep the range alive, not just with limited edition releases but with re-designs of some of the old Masters, such as the new Mudman models released in 2006, followed by new Gulfman models in 2007.
Three of the current Masters of G have been included in a new collection launched on February 2009, the Men In Rusty Black (MIRB) series. The watches under this theme, which include the Riseman (GW-9200MS), the Frogman (GW-200MS) and the Mudman (G-9000MS), are said to feature a military-inspired look.
- Antman, discontinued –
- Codename, discontinued –
- Fisherman, discontinued –
- Frogman, current models are GWF-1000 (atomic) and GF-1000 (non-atomic)
- Seaman, discontinued
- Gaussman, discontinued –
- Gulfman, current model is GW-9110 (atomic)
- Gulfmaster, current model is GWN-1000 (atomic)
- Lungman, discontinued –
- Mudman, current models are G-9000MS-1, GW-9300 (atomic) and G-9300 (non-atomic)
- Mudmaster, current model is GWG-1000 (atomic)
- Rangeman, current models are GW-9400-1 (Black), −3 (Khaki) 
- Raysman, discontinued –
- Revman, discontinued –
- Riseman, current models are GW-9200 (atomic) and G-9200 (non-atomic)
- Wademan, discontinued –
Master of G series watches are invariably amongst the largest G-Shock designs Casio produces, usually suited for those with larger wrists. They almost always named with a "man" suffix, after the initial Frogman model which itself was named for scuba divers. Three models, the Mudman, Gaussman, Raysman and Rangeman all feature a thick rubber outer layer that surrounds the buttons and case completely, ensuring they offer mud-resistance. The Gaussman was also ISO-certified anti-magnetic.
Most models consist of a steel case surrounded by a thick neoprene or polyurethane bezel and outer protection. All models except the earliest Frogmen feature Casio's Illuminator display lighting system and are water resistant to 20 atmospheres (20bar/200metres), and are thus suitable for scuba-diving except at depths requiring helium-oxygen gas.
Some of the modules incorporate highly advanced functions. The Riseman featured twin sensors that measured both temperature and atmospheric pressure, thus allowing it to serve as a barometer and altimeter. The Raysman was the first model to make use of Tough Solar technology to power its functions, the Wademan featured a digital compass, the Fisherman helped introduce the now-common tide graph and moonphase readouts, and the Antman was the first watch Casio made that received an atomic signal that calibrated its timekeeping with atomic clock transponders in Japan.
Today, it is not unusual for two or more of these features to be found in a single Master of G model i.e. the current GW-9200 Riseman has Tough Solar to power its radio-calibrated timekeeping and thermometer/altimeter/barometer functions; the GWF-1000 Frogman and GW-9110 Gulfman both feature solar power, radio timekeeping and tide and moon phase indicators. The current Mudman, designated as the GW-9300, has one of the most extensive feature sets by far, with mud/dust resistance, solar power, radio timekeeping, moon phase display, thermometer and digital compass functions.
Because they are no longer in production most of the Masters series command strong resale values; examples in NOS (New Old Stock) condition command a premium. Prices are sometimes higher outside Japan, not least because many models were produced only for the domestic market rather than for North America and Europe.
There have been several limited editions of the Masters series, and depending on their scarcity these command some of the highest prices for any of Casio watches. The Men in Black and Men in Yellow series are black and yellow versions of the Masters and typically command anywhere between two and three times the resale value of the regular versions. Some models such as the "Brazilian" Frogman and A.R.T.P.I Wademan are even scarcer and can command even higher prices, though their value is hard to predict as there are limited numbers and the price is largely determined by demand from individual collectors.
Although not always available, all models are usually valued at 500 USD or less, providing an affordable alternative to the collecting of prestige watches.