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Casio Analog GA-100 Series Mens Watch
Ref. GA-100-1A4ER
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Stepping up in the same colour and case shape
The GA-100 is a large-format G-Shock, with a 51.2mm polycarbonate resin case that sits 16.9mm deep and weighs 70g. Red accents punctuate the matte black exterior, and a mineral crystal covers a three-dial layout that combines physical hands with two reverse-LCD screens. The black resin strap fastens with a stainless steel double-pronged tang buckle. Calibre 5081 drives the watch, bringing a 1/1000-second stopwatch with a speed indicator, world time across 29 zones, five daily alarms, and an automatic calendar running to 2099. Water resistance is rated to 200 metres.
- Reference
- GA-100-1A4ER
- Brand
- Casio
- Collection
- G-Shock
- Case size
- 55mm
- Case material
- Resin
- Case shape
- Round
- Dial
- Black
- Crystal
- Mineral
- Movement
- Automatic
- Calibre
- 5081
- Functions
- Chronograph, GMT, Stopwatch, Alarm, Backlight, World time, Dual display
- Water resistance
- 200m
- Bracelet / strap
- Rubber strap
- Strap colour
- Black
- Clasp
- Buckle
- Retailer
- F.Hinds
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.
Also in 7 collections
This watch appears in the Casio G-Shock range (85), Back in Stock (2,812), Automatic Watches (1,549), Chronograph Watches (1,029), Watches 44mm and Over (711), Sports Watches (698) and Watches Under £100 (502).
Manufacturer’s guarantee
What the specifications mean
A mechanical watch built to be worn hard and got wet.
Strengths
- 200m water resistance, rated for actual diving
- Second time zone for travelling
- Sits in the lower half of Casio's range as we list it
Worth knowing
- 55mm is a large watch with real presence
Price history
This watch is currently at its lowest recorded price. It reached £110 on 10 August. Prices are checked every day, and we record any changes.
Casio Analog GA-100 Series alternatives
Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.
| Specification |  GA-100-1A4ER | 47511/BK |
|---|---|---|
| Price | £70 | £75 |
| Case size | 55mm | 51mm |
| Water resistance | 200m | — |
| Movement | Automatic | Automatic |
| Strap | Rubber strap | Silicone 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.
Water resistance explainedWill the glass scratch?
It can, over time. Mineral glass handles daily wear but will pick up fine scratches that sapphire would not.
Sapphire, mineral and acrylic comparedDoes it need a battery?
No. It is automatic — the motion of your wrist winds it, and there is no cell to replace.
Quartz, automatic and solar comparedIs 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.
Has the price changed recently?
It's currently at its lowest recorded price since we began tracking it. It's ranged between £70 and £110, today it's £70.
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