Casio F-91W vs Mido Ocean Star GMT
Casio's timepiece meets Mido's diver
Quick Verdict
The Casio F-91W (Under $50) offers Casio Digital Quartz (Battery) precision in the tier below the Mido Ocean Star GMT ($1,000–$1,500). The F-91W measures 35mm and is rated 30m (Splash Resistant). The Ocean Star GMT counters with Swiss Made craftsmanship and 200m (20 ATM) water resistance. Both are exceptional watches for their respective tiers.
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Specifications Compared
| Feature | Casio F-91W | Mido Ocean Star GMT |
|---|---|---|
| Price | Under $50 | $1,000–$1,500 |
| Case Size | 35mm | 44mm |
| Movement | Quartz Module 593 | Automatic Caliber 80 (Base ETA C07.661) |
| Caliber Type | Casio Digital Quartz (Battery) | Automatic (ETA C07.661 base) |
| Power Reserve | 7-Year Battery | 80 Hours |
| Water Resistance | 30m (Splash Resistant) | 200m (20 ATM) |
| Crystal | Acrylic | Sapphire with Double-sided AR |
| Case Material | Resin | Stainless Steel |
| Origin | Casio (Japan) | Swiss Made |
Category-by-Category Analysis
Design & Aesthetics
Casio's design language vs Mido's approach
The Casio F-91W features a Resin case at 35mm with Acrylic protection. The Mido Ocean Star GMT offers Stainless Steel construction at 44mm with Sapphire with Double-sided AR. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Quartz Module 593 vs Automatic Caliber 80 (Base ETA C07.661)
The F-91W runs the Quartz Module 593 (Casio Digital Quartz (Battery), 7-Year Battery power reserve) at standard frequency. The Ocean Star GMT uses the Automatic Caliber 80 (Base ETA C07.661) (Automatic (ETA C07.661 base), 80 Hours reserve) at 21,600 vph (3 Hz). The Ocean Star GMT offers a longer power reserve.
Wearability & Fit
35mm vs 44mm — different wrist presence
At 35mm, the F-91W wears more compactly on smaller wrists compared to the Ocean Star GMT at 44mm. Water resistance differs: 30m (Splash Resistant) vs 200m (20 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Casio F-91W sits at Under $50 and the Mido Ocean Star GMT at $1,000–$1,500. On the specs that outlast any price: the F-91W uses Acrylic with 7-Year Battery, against Sapphire with Double-sided AR and 80 Hours on the Ocean Star GMT. Service intervals are typically 5-7 years for both.
Water Resistance
30m (Splash Resistant) vs 200m (20 ATM)
The F-91W is rated to 30m (Splash Resistant) while the Ocean Star GMT handles 200m (20 ATM). The Ocean Star GMT offers superior water resistance.
Our Verdict
Casio
F-91W
Choose the Casio F-91W if you prioritize Casio Digital Quartz (Battery) engineering, Casio (Japan) craftsmanship, and 30m (Splash Resistant) water resistance. At Under $50, it delivers Quartz Module 593 with 7-Year Battery power reserve.
Check Price on AmazonMido
Ocean Star GMT
Choose the Mido Ocean Star GMT if you value Automatic (ETA C07.661 base) technology, Swiss Made heritage, and 44mm proportions. At $1,000–$1,500, the Automatic Caliber 80 (Base ETA C07.661) with 80 Hours power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Casio F-91W and Mido Ocean Star GMT represent two distinct approaches to fine watchmaking — the Casio bringing Casio (Japan) tradition while Mido delivers Swiss Made engineering.
Frequently Asked Questions
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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.