Omega Speedmaster Professional vs Casio G-Shock GA-B2100 CasiOak
Omega's chronograph meets Casio's diver
Quick Verdict
The Casio G-Shock GA-B2100 CasiOak ($100–$150) delivers Casio Quartz (Solar-Powered) technology in the tier below the Omega Speedmaster Professional ($5,000–$10,000). The G-Shock GA-B2100 CasiOak measures 45.4mm (48.5mm lug-to-lug, 11.9mm thick) and is rated 200m (20 ATM). The Speedmaster Professional justifies its premium with Swiss Made heritage and Manual-Winding Caliber 3861. Both represent excellent choices in the luxury watch category.
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Specifications Compared
| Feature | Omega Speedmaster Professional | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Price | $5,000–$10,000 | $100–$150 |
| Case Size | 42mm | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) |
| Movement | Manual-Winding Caliber 3861 | Quartz Module 5689 (Tough Solar + Bluetooth) |
| Caliber Type | In-House Manual-Winding Manufacture (Co-Axial) | Casio Quartz (Solar-Powered) |
| Power Reserve | 50 Hours | About 7 months on a full charge without light; about 18 months in power-saving (Casio) |
| Water Resistance | 50m (5 ATM) | 200m (20 ATM) |
| Crystal | Hesalite or Sapphire | Mineral Glass |
| Case Material | Stainless Steel | Carbon Core Guard Resin |
| Origin | Swiss Made | Made in Japan |
Category-by-Category Analysis
Design & Aesthetics
Omega's design language vs Casio's approach
The Omega Speedmaster Professional features a Stainless Steel case at 42mm with Hesalite or Sapphire protection. The Casio G-Shock GA-B2100 CasiOak offers Carbon Core Guard Resin construction at 45.4mm (48.5mm lug-to-lug, 11.9mm thick) with Mineral Glass. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Manual-Winding Caliber 3861 vs Quartz Module 5689 (Tough Solar + Bluetooth)
The Speedmaster Professional runs the Manual-Winding Caliber 3861 (In-House Manual-Winding Manufacture (Co-Axial), 50 Hours power reserve) at 21,600 vph (3 Hz) frequency. The G-Shock GA-B2100 CasiOak uses the Quartz Module 5689 (Tough Solar + Bluetooth) (Casio Quartz (Solar-Powered), About 7 months on a full charge without light; about 18 months in power-saving (Casio) reserve) at standard. The Speedmaster Professional edges ahead on power reserve.
Wearability & Fit
42mm vs 45.4mm (48.5mm lug-to-lug, 11.9mm thick) — different wrist presence
At 42mm, the Speedmaster Professional wears more compactly on smaller wrists compared to the G-Shock GA-B2100 CasiOak at 45.4mm (48.5mm lug-to-lug, 11.9mm thick). Water resistance differs: 50m (5 ATM) vs 200m (20 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Omega Speedmaster Professional sits at $5,000–$10,000 and the Casio G-Shock GA-B2100 CasiOak at $100–$150. On the specs that outlast any price: the Speedmaster Professional uses Hesalite or Sapphire with 50 Hours, against Mineral Glass and About 7 months on a full charge without light; about 18 months in power-saving (Casio) on the G-Shock GA-B2100 CasiOak. Service intervals are typically 5-7 years for both.
Water Resistance
50m (5 ATM) vs 200m (20 ATM)
The Speedmaster Professional is rated to 50m (5 ATM) while the G-Shock GA-B2100 CasiOak handles 200m (20 ATM). The G-Shock GA-B2100 CasiOak offers superior water resistance.
Materials Face-Off
| Component | Omega Speedmaster Professional | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Co-Axial Caliber 3861 | Manual-wind chronograph with Co-Axial escapement (George Daniels design, licensed 1999). Si14 silicon balance spring, free-sprung balance, 234 components, 26 jewels | Casio's proprietary monocoque case technology integrating carbon fibers into fine resin. The carbon fibers dramatically raise the tensile strength and modulus of elasticity of the case structure, allowing the GA-2100 to achieve an 11.8mm thickness — the thinnest analog G-Shock at launch — while maintaining full 10m drop impact resistance. Total case weight: 51g. |
| Hesalite Crystal | Hardened acrylic (Mohs ~2–3) with embossed central Omega logo — the NASA flight-qualified specification Mohs 2.5 | Flat mineral glass with Mohs hardness ~6. Thermally tempered for impact resistance — flexes under force rather than shattering like sapphire. Not scratch-proof, but replacement crystals cost ~$10. |
| Silicon Balance Spring (Si14) | Omega's proprietary Si14 silicon hairspring — in series production since 2008 | Durable urethane polymer resistant to sweat, saltwater, UV radiation, and skin oils. Features quick-release spring bars. Known to last 5–10 years with daily wear before degradation. |
| Aluminum Tachymeter Bezel | Fixed black anodized aluminum with white tachymeter scale. Preserves the "DOT OVER NINETY" detail from the Apollo 11–era watches | Secured by 4 Phillips screws for 200m (20 ATM) water resistance. The GA-B2100 is Tough Solar: a rechargeable cell topped up by any light, so there is no coin cell to swap. Casio rates a full charge at about seven months of normal use without light, and about eighteen months in power-saving. |
| Stainless Steel Case | 42mm asymmetric case with integrated crown guards (added in 1964 for the 105.012 — the reference Buzz Aldrin wore on the Moon) | The luxury MRG-B2100 variant ($3,500+), hand-assembled at Yamagata Casio's Premium Production Line (PPL) by certified "Medalist" craftsmen, uses Cobarion® (cobalt-chromium alloy, 4× harder than pure titanium) bezels and DAT55G titanium (3× harder than pure titanium) bracelet links. |
Cost of Ownership Compared
Who Should Pick Which
Pick the Omega Speedmaster Professional if…
- History and heritage enthusiasts — the only watch worn on the Moon, with NASA documentation to prove it
- METAS Master Chronometer accuracy at sub-$8,000 — antimagnetic to 15,000 gauss, 0/+5 sec/day
- Chronograph lovers — the manual-wind ritual and hand-wound feel is deeply satisfying
- Value seekers at grey market $5,200–$5,500 — one of the cheapest 5-figure-quality chronographs from a top-tier maison
- Available off-the-shelf — walk into any Omega boutique and buy one today (no Rolex-style waitlist)
Pick the Casio G-Shock GA-B2100 CasiOak if…
- Anyone wanting an indestructible daily beater under $100 with serious design credibility
- Water sports enthusiasts — 200m WR with G-Shock shockproofing
- Watch modding enthusiasts — massive aftermarket ecosystem of metal conversion kits
- High-end collectors needing a dedicated beater alongside their luxury pieces
Omega Speedmaster Professional
- Hesalite scratches — acrylic at Mohs ~2–3 is dramatically softer than sapphire. Polishes out with PolyWatch in 5 minutes, but it's high-maintenance for desk-diving wear
- No screw-down crown, 50m water resistance — this is a NASA chronograph, not a dive watch. Shower-safe, swim-cautious, never deep water
- Manual wind — not for the set-and-forget buyer. Daily winding is part of the ritual; some find it charming, some find it inconvenient
- Wears thick at 13.18mm with a proud bezel — reads as 43–44mm visually because of the broad lug profile
Casio G-Shock GA-B2100 CasiOak
- Stealth-black legibility deficit: The GA2100-1A1 has absolutely no Neobrite luminescent paint on hands or indices. Low-light readability is poor — you must rely entirely on the Double LED Super Illuminator.
- Mineral glass scratches: Not sapphire. Daily beater use will accumulate minor scuffs over time. Replacement crystals are cheap (~$10) but require caseback removal.
- Tiny digital subdisplay: The LCD window at 4:30 is small and genuinely difficult to read for anyone with less than perfect vision. The Hand-Shift feature (sweeps hands to 7:35 position to clear the LCD) helps but isn't a substitute for a full digital display.
- Module 5689 is quartz: For mechanical-watch purists, this is a non-starter. For everyone else, it's a feature — better accuracy (±15 sec/month), no winding, no expensive servicing, and solar charging that never needs a battery change.
Our Verdict
Omega
Speedmaster Professional
Choose the Omega Speedmaster Professional if you prioritize In-House Manual-Winding Manufacture (Co-Axial) engineering, Swiss Made craftsmanship, and 50m (5 ATM) water resistance. At $5,000–$10,000, it delivers Manual-Winding Caliber 3861 with 50 Hours power reserve.
Check Price on AmazonCasio
G-Shock GA-B2100 CasiOak
Choose the Casio G-Shock GA-B2100 CasiOak if you value Casio Quartz (Solar-Powered) technology, Made in Japan heritage, and 45.4mm (48.5mm lug-to-lug, 11.9mm thick) proportions. At $100–$150, the Quartz Module 5689 (Tough Solar + Bluetooth) with About 7 months on a full charge without light; about 18 months in power-saving (Casio) power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Omega Speedmaster Professional and Casio G-Shock GA-B2100 CasiOak represent two distinct approaches to fine watchmaking — the Omega bringing Swiss Made tradition while Casio delivers Made in Japan engineering.
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