Casio F-91W vs Seiko Presage SSA425 Open Heart
Two timepieces compared — Under $50 vs $250–$500
Quick Verdict
The Casio F-91W (Under $50) offers Casio Digital Quartz (Battery) precision in the tier below the Seiko Presage SSA425 Open Heart ($250–$500). The F-91W measures 35mm and is rated 30m (Splash Resistant). The Presage SSA425 Open Heart counters with Made in Japan craftsmanship and 50m (5 ATM) water resistance. Both are exceptional timepieces for their respective tiers.
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Specifications Compared
| Feature | Casio F-91W | Seiko Presage SSA425 Open Heart |
|---|---|---|
| Price | Under $50 | $250–$500 |
| Case Size | 35mm | 40.5mm |
| Movement | Quartz Module 593 | Automatic Caliber 4R38 |
| Caliber Type | Casio Digital Quartz (Battery) | Seiko In-House Automatic |
| Power Reserve | 7-Year Battery | 41 Hours |
| Water Resistance | 30m (Splash Resistant) | 50m (5 ATM) |
| Crystal | Acrylic | Hardlex Crystal |
| Case Material | Resin | Stainless Steel |
| Origin | Casio (Japan) | Made in Japan |
Category-by-Category Analysis
Design & Aesthetics
Casio's design language vs Seiko's approach
The Casio F-91W features a Resin case at 35mm with Acrylic protection. The Seiko Presage SSA425 Open Heart offers Stainless Steel construction at 40.5mm with Hardlex Crystal. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Quartz Module 593 vs Automatic Caliber 4R38
The F-91W runs the Quartz Module 593 (Casio Digital Quartz (Battery), 7-Year Battery power reserve) at standard frequency. The Presage SSA425 Open Heart uses the Automatic Caliber 4R38 (Seiko In-House Automatic, 41 Hours reserve) at 21,600 vph (3 Hz). The Presage SSA425 Open Heart offers a longer power reserve.
Wearability & Fit
35mm vs 40.5mm — different wrist presence
At 35mm, the F-91W wears more compactly on smaller wrists compared to the Presage SSA425 Open Heart at 40.5mm. Water resistance differs: 30m (Splash Resistant) vs 50m (5 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Casio F-91W sits at Under $50 and the Seiko Presage SSA425 Open Heart at $250–$500. On the specs that outlast any price: the F-91W uses Acrylic with 7-Year Battery, against Hardlex Crystal and 41 Hours on the Presage SSA425 Open Heart. Service intervals are typically 5-7 years for both.
Water Resistance
30m (Splash Resistant) vs 50m (5 ATM)
The F-91W is rated to 30m (Splash Resistant) while the Presage SSA425 Open Heart handles 50m (5 ATM). The Presage SSA425 Open Heart 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 AmazonSeiko
Presage SSA425 Open Heart
Choose the Seiko Presage SSA425 Open Heart if you value Seiko In-House Automatic technology, Made in Japan heritage, and 40.5mm proportions. At $250–$500, the Automatic Caliber 4R38 with 41 Hours power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Casio F-91W and Seiko Presage SSA425 Open Heart represent two distinct approaches to the timepiece category — the Casio bringing Casio (Japan) tradition while Seiko 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.