Casio G-Shock GA-B2100 CasiOak vs Timex Marlin Automatic 40mm
Casio's diver meets Timex's timepiece
Quick Verdict
The Casio G-Shock GA-B2100 CasiOak ($100–$150) offers Casio Quartz (Solar-Powered) precision in the tier below the Timex Marlin Automatic 40mm ($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 Marlin Automatic 40mm counters with Made in Japan (Movement) craftsmanship and 30m (3 ATM) water resistance. Both are exceptional watches for their respective tiers.
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Specifications Compared
| Feature | Casio G-Shock GA-B2100 CasiOak | Timex Marlin Automatic 40mm |
|---|---|---|
| Price | $100–$150 | $250–$500 |
| Case Size | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) | 40mm |
| Movement | Quartz Module 5689 (Tough Solar + Bluetooth) | Automatic Miyota 8205 |
| Caliber Type | Casio Quartz (Solar-Powered) | Miyota Automatic |
| Power Reserve | About 7 months on a full charge without light; about 18 months in power-saving (Casio) | 40 Hours |
| Water Resistance | 200m (20 ATM) | 30m (3 ATM) |
| Crystal | Mineral Glass | Mineral Crystal |
| Case Material | Carbon Core Guard Resin | Stainless Steel |
| Origin | Made in Japan | Made in Japan (Movement) |
Category-by-Category Analysis
Design & Aesthetics
Casio's design language vs Timex's approach
The Casio G-Shock GA-B2100 CasiOak features a Carbon Core Guard Resin case at 45.4mm (48.5mm lug-to-lug, 11.9mm thick) with Mineral Glass protection. The Timex Marlin Automatic 40mm offers Stainless Steel construction at 40mm with Mineral Crystal. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Quartz Module 5689 (Tough Solar + Bluetooth) vs Automatic Miyota 8205
The G-Shock GA-B2100 CasiOak runs 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) power reserve) at standard frequency. The Marlin Automatic 40mm uses the Automatic Miyota 8205 (Miyota Automatic, 40 Hours reserve) at 21,600 vph (3 Hz). The Marlin Automatic 40mm offers a longer power reserve.
Wearability & Fit
45.4mm (48.5mm lug-to-lug, 11.9mm thick) vs 40mm — different wrist presence
At 45.4mm (48.5mm lug-to-lug, 11.9mm thick), the G-Shock GA-B2100 CasiOak has a bolder wrist presence compared to the Marlin Automatic 40mm at 40mm. Water resistance differs: 200m (20 ATM) vs 30m (3 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Casio G-Shock GA-B2100 CasiOak sits at $100–$150 and the Timex Marlin Automatic 40mm at $250–$500. On the specs that outlast any price: the G-Shock GA-B2100 CasiOak uses Mineral Glass with About 7 months on a full charge without light; about 18 months in power-saving (Casio), against Mineral Crystal and 40 Hours on the Marlin Automatic 40mm. Service intervals are typically 5-7 years for both.
Water Resistance
200m (20 ATM) vs 30m (3 ATM)
The G-Shock GA-B2100 CasiOak is rated to 200m (20 ATM) while the Marlin Automatic 40mm handles 30m (3 ATM). The G-Shock GA-B2100 CasiOak is better suited for water activities.
Our Verdict
Casio
G-Shock GA-B2100 CasiOak
Choose the Casio G-Shock GA-B2100 CasiOak if you prioritize Casio Quartz (Solar-Powered) engineering, Made in Japan craftsmanship, and 200m (20 ATM) water resistance. At $100–$150, it delivers 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.
Check Price on AmazonTimex
Marlin Automatic 40mm
Choose the Timex Marlin Automatic 40mm if you value Miyota Automatic technology, Made in Japan (Movement) heritage, and 40mm proportions. At $250–$500, the Automatic Miyota 8205 with 40 Hours power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Casio G-Shock GA-B2100 CasiOak and Timex Marlin Automatic 40mm represent two distinct approaches to fine watchmaking — the Casio bringing Made in Japan tradition while Timex delivers Made in Japan (Movement) 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.