A true technical gem...

It’s not unreasonable to have minimum design and capability expectations from a G-Shock, so when one delivers much more than the technical basics it is always interesting and worthy of closer scrutiny. Back in the 1990s Casio took a bold step and released the G-100. On paper, this seemed to have all the normal G-specs such as 200m water resistance, shock resistance and various digital tools. The big difference was that the watch was analogue, with a small digital sub-screen. It turned the G-world on its head as up till its release, G-Shocks had traditionally been chunky all digital affairs. The G-100 was (is) a great watch which benefitted from a revised movement to allow an analogue machine to have the levels of resistance we had come to enjoy from the standard LCD models.

Since the advent of the G-100 analogue G-Shocks have been a large part of the Casio portfolio and today they stand shoulder to shoulder with the classic Gs as highly desirable watches. One such example is the GA-100, an early model in the Gravitymaster Range. This is no ordinary G and within its impressive façade lurks a technical marvel that offers so many good features that it should be considered a classic along with legends like the “Stargate” G-Shock DW-8300.

It is fair to say that the design of some of the more extreme G-Shocks are not always to everyone’s taste. A good friend of the magazine owns a gold GA-400GB. It’s a blingy fashion watch, pure and simple, but it still manages to list some impressive technical specs and underneath the rather garish exterior beats the heart of a G. However, some of us prefer the more subtle tool watch G-Shocks which look like they have been lifted straight from the cockpit of the Space Shuttle and the GA-100 is exactly such a model.

Casio G-Shock GA-100B-7AER

The Casio G-Shock GA-100B-7AER - Image credit WatchGecko.

The variant we looked at was the GA-100B-7AER which is arguably one of the most striking. It comes in pure white, case and strap, with the exception of the blue impact lining peeking through. It is visually impressive and the attention to detail is sublime.

First impressions are of a large unit and at 51mm diameter, this is no dress watch. However, it does not “wear” big, and this is testimony to the clever design of the case and strap. Casio has really excelled with this model. It somehow just feels smaller than many standard G-Shocks and will sit comfortably on ever a smaller wrist. At a total weight of 70g, you will never feel the watch is there.

If we look in detail at the design of the GA-100 there is so much to observe that this watch will give you many months of viewing pleasure. The dial is excitingly proportioned and looks like an aircraft cockpit. Three sub-dials dominate the upper half. Two of these are digital and show the status of essential watch functions and also stopwatch subdivisions. The middle dial is analogue and bears a striking resemblance to a speedometer. More on this later.

The lower half of the dial has two angular digital screens which have a plethora of displays depending on what function you are using. One even has the intriguing word MACH on it…

As a default, the screens show the date/day/seconds. The 7AER we analysed had an inverted LCD which really enhanced the overall look of the dial and made it more cohesive. Casio’s inverted LCD is a divisive technical characteristic. It does look cleaner and (we are told) uses less power but it can be hard to see in low light. On this particular watch, it looks good. The main reason is that in the centre of the dial are two skeletonised analogue hands which are the principal method of telling the time on the GA-100. The inverted LCD blends into the dark dial and makes the white hands really stand out. Legibility was remarkably good for such a complex dial. It reminds you a little of a Breitling Aerospace but with a much-reduced price!

Casio G-Shock GA-100B-7AER

Dial shot of the Casio G-Shock GA-100B-7AER - Image credit WatchGecko.

The indices for the hands are clear and the minute track on the rehaut is bold. The dial itself has been thought about very carefully and any remaining real estate which does not have a function is decorated in a chunky embossed 3D hatch pattern which adds to the tool watch feel. The upshot is a very attractive G-Shock that will really challenge people’s perceptions of the more complex models in the brand.

The mineral glass lens is well recessed and thoroughly protected by a raised polymer guard which is part of the main watch case. Like many Gs, the GA-100 case comprises a stainless-steel inner case coated with a resin outer, in dual colours with the GA-100. This case joins seamlessly with an identical feel and colour strap.

The four push buttons are well protected, and the case back is screwed in place. Unsurprisingly this comprehensive package offers the full and expected G-Shock 200m water resistance.

Casio G-Shock GA-100B-7AER caseback

Caseback of the Casio G-Shock GA-100B-7AER - Image credit WatchGecko.

Regarding functions, the watch does everything you would expect from it with a few surprises. There is the mandatory stopwatch, count-down timer, alarms, and a worldwide dual time display. The stopwatch is the first function to divert from the norm as it measures up to 100 hours rather than the more normal lower levels found on digital watches. This makes it more akin to an elapsed mission timer as you can accurately cover considerable periods in a manner that is normally the purview of Astronaut watches like the Omega X-33. The stopwatch itself also has a 1/1000 of a second capability and to observe the 1000s of a second flashing round in the digital screen is quite impressive.

However, the best feature of the GA-100 is its unique take on a tachymeter which permits, using a combination of the analogue upper sub-dial and the digital screens, the measurement of the speed of an object between two known points. Do you recall we mentioned the MACH window? Well, this is a digital indicator which activates if the object being timed is travelling over the maximum measurable speed of 1226 units per hour. Once you learn how to use the tachymeter it is a lot of fun to play with and you can accurately measure speeds as slow as walking pace or as fast as a jet plane. Ok, granted, it is highly unlikely that most of us will push this function to the MACH limits, but the Gravitymaster range was originally developed in response to requests from professional pilots, so this function has sound origins.

The Casio G-Shock GA-100B-7AER LED dial - Image credit WatchGecko.

Low visibility and night use are solved not with the expected blue electro-lume synonymous with Casios, but with a single LED fitted at the bottom of the dial. This orange up-lit glow softly highlights all the aforementioned 3D dial and hands. It uses very little power and is highly effective and attractive to look at.

To round off the impressive specs of the watch Casio has pulled out all the stops and given the GA-100 an anti-magnetic capability in line with ISO 764:2002. To pass this test a watch must resist exposure to a direct current magnetic field of 4800 A/m and retain accuracy to ±30 seconds per day. Lots of watches have this capability and some of course like the Rolex Milgauss and Omega Aqua-Terra resist much higher forces but it is exciting to see the words ANTIMAGNETIC engraved on the case back of the GA-100 and it serves to give you even more confidence in the machine.

In summary:

The GA-100 Gravitymaster is in every measurable way a superior watch which can easily be found new for under £100. How you can buy this level of performance and technical fun for such a small amount is frankly beyond us which makes the GA-100 a gem to own. There are upwards of 30 different models in the range which offer colours and finishes to suit every taste. Whether you are a seasoned G fan or new to the genre we think the GA-100 is a “must-have” watch. Once you take the time to understand the functions, the watch becomes so much more than the sum of its parts and will be a standout part of your collection.

Technical specifications of the Casio GA-100

  • Case / bezel material: Resin
  • Resin Band
  • Magnetic Resistant to ISO 764
  • Shock Resistant
  • Mineral Glass
  • 200-meter water resistance
  • LED light: Auto light switch, selectable illumination duration (1.5 seconds or 3 seconds), afterglow
  • World time: 29 time zones (48 cities + coordinated universal time), daylight saving on/off, Home city / World time city swapping
  • 1/1000-second stopwatch with measuring capacity: 99:59’59.999”
  • Measuring modes: Elapsed time, lap time, split time
  • Tachymeter: Speed (0 to 1998 units / hour), Distance input (0.0 to 99.9) with MACH indicator (speed exceeding 1225 units / hour)
  • Countdown timer: Measuring unit: 1 second
  • Countdown range: 24 hours
  • Countdown start time setting range: 1 minute to 24 hours (1-minute increments and 1-hour increments)
  • Other: Auto-repeat5 daily alarms (with 1 snooze alarm)
  • Hourly time signal
  • Full auto-calendar (to the year 2099)
  • 12/24-hour format
  • Analogue: 2 hands (hour, minute (hand moves every 20 seconds)), 1 dial (speed)
  • Digital: Hour, minute, second, pm, month, date, day
  • Accuracy: ±15 seconds per month
  • Approx. battery life: 2 years using quality CR1220
  • Size of case: 55×51.2×16.9mm
  • Total weight: 70g