Citizen Tsuyosa Automatic (Green Dial) vs Casio G-Shock GA-B2100 CasiOak
Citizen's timepiece 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 Citizen Tsuyosa Automatic (Green Dial) ($250–$500). The G-Shock GA-B2100 CasiOak measures 45.4mm (48.5mm lug-to-lug, 11.9mm thick) and is rated 200m (20 ATM). The Tsuyosa Automatic (Green Dial) justifies its premium with Made in Japan heritage and Automatic Caliber 8210. Both represent excellent choices in the luxury watch category.
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Specifications Compared
| Feature | Citizen Tsuyosa Automatic (Green Dial) | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Price | $250–$500 | $100–$150 |
| Case Size | 40mm | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) |
| Movement | Automatic Caliber 8210 | Quartz Module 5689 (Tough Solar + Bluetooth) |
| Caliber Type | Citizen/Miyota In-House Automatic | Casio Quartz (Solar-Powered) |
| Power Reserve | 40 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 | Sapphire Crystal with Cyclops | Mineral Glass |
| Case Material | Stainless Steel | Carbon Core Guard Resin |
| Origin | Made in Japan | Made in Japan |
Category-by-Category Analysis
Design & Aesthetics
Citizen's design language vs Casio's approach
The Citizen Tsuyosa Automatic (Green Dial) features a Stainless Steel case at 40mm with Sapphire Crystal with Cyclops 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
Automatic Caliber 8210 vs Quartz Module 5689 (Tough Solar + Bluetooth)
The Tsuyosa Automatic (Green Dial) runs the Automatic Caliber 8210 (Citizen/Miyota In-House Automatic, 40 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 Tsuyosa Automatic (Green Dial) edges ahead on power reserve.
Wearability & Fit
40mm vs 45.4mm (48.5mm lug-to-lug, 11.9mm thick) — different wrist presence
At 40mm, the Tsuyosa Automatic (Green Dial) 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 Citizen Tsuyosa Automatic (Green Dial) sits at $250–$500 and the Casio G-Shock GA-B2100 CasiOak at $100–$150. On the specs that outlast any price: the Tsuyosa Automatic (Green Dial) uses Sapphire Crystal with Cyclops with 40 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 Tsuyosa Automatic (Green Dial) 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.
Our Verdict
Citizen
Tsuyosa Automatic (Green Dial)
Choose the Citizen Tsuyosa Automatic (Green Dial) if you prioritize Citizen/Miyota In-House Automatic engineering, Made in Japan craftsmanship, and 50m (5 ATM) water resistance. At $250–$500, it delivers Automatic Caliber 8210 with 40 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 Citizen Tsuyosa Automatic (Green Dial) and Casio G-Shock GA-B2100 CasiOak represent two distinct approaches to fine watchmaking — the Citizen bringing Made in Japan tradition while Casio delivers Made in Japan engineering.
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How This Page Was Made
Our comparisons are generated from a hand-maintained specification database and reviewed under our editorial standards. We use AI tools to assemble pages from that data. We don’t invent specs: every number traces back to the database, and when we correct an entry, the fix is applied site-wide. As an Amazon Associate, The Horologist earns from qualifying purchases.