Tap the image to enlarge
Casio G-SHOCK GBM-2100A-1A2ER Solar Blue Dial Resin Strap Watch - W17566
Ref. GBM-2100A-1A2ER
Sits in Casio’s upper tier here — more premium than three quarters of the Casio watches we list, which start at £25.
Price range £25 to £919 across 129 Casio watches in stock.The GBM-2100A belongs to Casio's Metal Covered series — the line that answered the question of what a G-SHOCK would look like if it borrowed the octagonal geometry of a certain Swiss sports watch and then resolved it through Casio's own engineering logic. The outer bezel is polished stainless steel; the inner case remains bio-based resin, which is how it keeps the shock resistance the name requires. The blue dial is not painted but vapour-deposited, which gives it a depth that shifts noticeably under different light. At 11.9mm thick and 72 grams, this is not what a stainless sports watch usually feels like. It sits flat and disappears on the wrist in a way that steel of this rating rarely does. The Bluetooth link to Casio's smartphone app handles time-zone and alarm management without menu-diving, and Tough Solar means the module powers itself from ambient light indefinitely under normal wear. The strap integrates cleanly into the case and uses push-pin quick-release lugs, so swapping it takes seconds rather than a spring-bar tool.
- Reference
- GBM-2100A-1A2ER
- Brand
- Casio
- Collection
- G-Shock
- Case size
- 44.4mm
- Case thickness
- 11.9mm
- Lug width
- 16mm
- Case material
- Resin
- Case shape
- Octagonal
- Dial
- Blue
- Crystal
- Mineral
- Movement
- Solar
- Functions
- Day-date, Stopwatch, Countdown timer, Alarm, Backlight, World time, 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
- 49.3mm
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
Best of 2 retailers
What the specifications mean
A watch built to be worn hard and got wet.
Strengths
- 200m water resistance, rated for actual diving
- 49.3mm lug-to-lug keeps the 44.4mm case wearable
- Luminous hands and markers for low light
- Second time zone for travelling
- One of Casio's more premium watches
Worth knowing
- 44.4mm sits at the larger end
Compare alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification |  GBM-2100A-1A2ER |  RA-TX0202B10B |  MTRH2S601 |
|---|---|---|---|
| Price | £229 | £219 | £250 |
| Case size | 44.4mm | 42.8mm | 44mm |
| Water resistance | 200m | 200m | 100m |
| Movement | Solar | Solar | Solar |
| Strap | Rubber strap | Stainless steel bracelet | Stainless steel bracelet |
| 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.
What size strap does it take?
16mm. Any strap of that width will fit, and on most modern watches quick-release bars make the swap a two-minute job with no tools.
Will it fit my wrist?
Lug-to-lug is 49.3mm, 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
Both F.Hinds and Goldsmiths list it at £229, so choose on delivery and warranty rather than price.
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.
You may also like
In stock, and close on style and price
