Bulova Classic Automatic 98A139 vs Casio G-Shock GA-B2100 CasiOak
Bulova'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 Bulova Classic Automatic 98A139 ($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 Classic Automatic 98A139 justifies its premium with Japanese Movement heritage and Automatic, 21 Jewels. Both represent excellent choices in the luxury watch category.
Transparency — We earn a small commission on purchases made through our Amazon links. This doesn't affect our editorial independence.
Specifications Compared
| Feature | Bulova Classic Automatic 98A139 | Casio G-Shock GA-B2100 CasiOak |
|---|---|---|
| Price | $250–$500 | $100–$150 |
| Case Size | 45mm | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) |
| Movement | Automatic, 21 Jewels | Quartz Module 5689 (Tough Solar + Bluetooth) |
| Caliber Type | Self-Winding Automatic | Casio Quartz (Solar-Powered) |
| Power Reserve | — | About 7 months on a full charge without light; about 18 months in power-saving (Casio) |
| Water Resistance | 30m (3 ATM) | 200m (20 ATM) |
| Crystal | Domed Crystal | Mineral Glass |
| Case Material | Black Ion-Plated Stainless Steel | Carbon Core Guard Resin |
| Origin | Japanese Movement | Made in Japan |
Category-by-Category Analysis
Design & Aesthetics
Bulova's design language vs Casio's approach
The Bulova Classic Automatic 98A139 features a Black Ion-Plated Stainless Steel case at 45mm with Domed Crystal 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, 21 Jewels vs Quartz Module 5689 (Tough Solar + Bluetooth)
The Classic Automatic 98A139 runs the Automatic, 21 Jewels (Self-Winding Automatic, standard power reserve) at standard 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 G-Shock GA-B2100 CasiOak offers a longer power reserve.
Wearability & Fit
45mm vs 45.4mm (48.5mm lug-to-lug, 11.9mm thick) — different wrist presence
At 45mm, the Classic Automatic 98A139 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: 30m (3 ATM) vs 200m (20 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Bulova Classic Automatic 98A139 sits at $250–$500 and the Casio G-Shock GA-B2100 CasiOak at $100–$150. On the specs that outlast any price: the Classic Automatic 98A139 uses Domed Crystal with a standard reserve, 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
30m (3 ATM) vs 200m (20 ATM)
The Classic Automatic 98A139 is rated to 30m (3 ATM) while the G-Shock GA-B2100 CasiOak handles 200m (20 ATM). The G-Shock GA-B2100 CasiOak offers superior water resistance.
Our Verdict
Bulova
Classic Automatic 98A139
Choose the Bulova Classic Automatic 98A139 if you prioritize Self-Winding Automatic engineering, Japanese Movement craftsmanship, and 30m (3 ATM) water resistance. At $250–$500, it delivers Automatic, 21 Jewels with solid 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 Bulova Classic Automatic 98A139 and Casio G-Shock GA-B2100 CasiOak represent two distinct approaches to fine watchmaking — the Bulova bringing Japanese Movement tradition while Casio delivers Made in Japan engineering.
Frequently Asked Questions
More Comparisons
Explore These Watches
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.