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Casio G-Shock GA-B2100-1AER Bluetooth Solar Black Strap Watch - W17317
Ref. GA-B2100-1AER
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Stepping up in the same dial colour
The GA-B2100 began life as the GA-2100, a battery-powered watch that accumulated an unlikely following among people who noticed that its octagonal bezel recalled certain expensive Swiss sports watches — hence the community nickname "CasiOak" that followed it everywhere. This model is the direct successor: the same silhouette, now rebuilt around a solar cell and Bluetooth pairing to a phone, which keeps it perpetually charged and perpetually accurate without any intervention from the owner. At 11.9mm thick and 52 grams, it is strikingly flat and light for something rated to 200 metres and built around Carbon Core Guard internals. The case disappears under a cuff the way most resin sports watches do not, and the weight is barely perceptible through a day's wear. The dial has been quietly reworked from the original: where the GA-2100 had a weekday sub-dial at nine o'clock, this version replaces it with a function and power indicator — a small but meaningful change that tells you the solar cell is doing its job. When the light fails, a double LED system illuminates the analogue face and the digital window independently, so the Neobrite on the hands is a supplement rather than the last resort.
- Reference
- GA-B2100-1AER
- Brand
- Casio
- Collection
- G-Shock
- Case size
- 45.4mm
- Case thickness
- 11.9mm
- Case material
- Resin
- Case shape
- Octagonal
- Dial
- Black
- Crystal
- Mineral
- Movement
- Solar
- Functions
- Chronograph, Day-date, Stopwatch, Countdown timer, Alarm, Backlight, World time, Perpetual calendar, Solar powered, Bluetooth, Dual display
- Water resistance
- 200m
- Bracelet / strap
- Rubber strap
- Strap colour
- Black
- Clasp
- Buckle
- Lume
- Luminous
- Retailer
- F.Hinds
Additional specifications
- Lug-to-lug
- 48.5mm
- Strap
- Interchangeable
Learn more about Casio
Tadao Kashio founded Kashio Seisakujo in Tokyo in 1946 as a machine shop. The company's first success was a finger ring that held a cigarette, and its second was the 14-A of 1957 — the world's first all-electric compact calculator, which used solenoids rather than gears.
Casio entered watchmaking in 1974 with the Casiotron, a digital watch with an automatic calendar that knew the varying lengths of months. The company approached watches as an electronics manufacturer rather than a horological one, and that difference produced the G-Shock.
The G-Shock came from a single engineer, Kikuo Ibe, who broke a watch his father had given him and set out to build one that could not break. The specification was three tens: survive a ten-metre drop, ten bars of water pressure, and ten years of battery life. It took over two hundred prototypes, and the solution was suspending the module inside the case on a cushioned internal structure rather than mounting it rigidly. The DW-5000C shipped in 1983.
It became one of the most durable product designs in any category, adopted by militaries, emergency services, and skateboarders alike, and Casio has since added solar charging, radio and GPS timekeeping, Bluetooth, and full-metal and carbon variants.
Casio also produces the Edifice, Pro Trek, and Oceanus lines, and remains an independent Japanese public company.
- 1946
- Tadao Kashio founds the company in Tokyo.
- 1974
- The Casiotron is Casio's first digital watch.
- 1983
- The G-Shock DW-5000C survives Kikuo Ibe's three-tens brief.
- 1994
- The Frogman extends G-Shock to ISO dive certification.
Manufacturer’s guarantee
What the specifications mean
A watch built to be worn hard and got wet.
Strengths
- 200m water resistance, rated for actual diving
- 48.5mm lug-to-lug keeps the 45.4mm case wearable
- Luminous hands and markers for low light
- Second time zone for travelling
Worth knowing
- 45.4mm is a large watch with real presence
Compare alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification | GA-B2100-1AER |  R8873645001 |  HB1514031 |
|---|---|---|---|
| Price | £129 | £159 | £189 |
| Case size | 45.4mm | 44mm | 44mm |
| Water resistance | 200m | 50m | 50m |
| Movement | Solar | Solar | Solar |
| Strap | Rubber strap | Stainless steel bracelet | Leather strap |
| This watch |
|
|
Your new watch
Frequently asked questions, and things you should know about this watch
Can I swim with it?
Yes. At 200m it is rated for swimming, snorkelling and recreational diving.
Will the glass scratch?
It can, over time. Mineral glass handles daily wear but will pick up fine scratches that sapphire would not.
Does it need a battery?
No. It charges from light, and the cell behind that is designed to last a decade or more.
Will it fit my wrist?
Lug-to-lug is 48.5mm, which suits wrists from roughly 16.5cm (6½ inches) upward.
Lug-to-lug decides fit more than case diameter does.
Is it a men's or women's watch?
Listed as men's.
Cheapest place to buy
F.Hinds is the only UK retailer we track stocking this reference, so there is nothing to compare it against today.
Who are F.Hinds?
F.Hinds has been run by the same family since 1856 and is now in its fifth generation, with more than 115 shops across England and Wales. They are a member of the Responsible Jewellery Council and an Authorised Diamond Dealer.
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