Head-to-Head Comparison

Updated September 5, 2026

Casio F-91W vs Seiko Prospex 62MAS Modern Re-interpretation

Casio's timepiece meets Seiko's diver

Quick Verdict

The Casio F-91W (Under $50) offers Casio Digital Quartz (Battery) precision in the tier below the Seiko Prospex 62MAS Modern Re-interpretation ($1,000–$1,500). The F-91W measures 35mm and is rated 30m (Splash Resistant). The Prospex 62MAS Modern Re-interpretation counters with Made in Japan craftsmanship and 200m (20 ATM) water resistance. Both are exceptional watches for their respective tiers.

CasioF-91WUnder $50 Check price SeikoProspex 62MAS Modern Re-interpretation$1,000–$1,500 Check price

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Casio

F-91W

Under $50

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Seiko

Prospex 62MAS Modern Re-interpretation

$1,000–$1,500

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Specifications Compared

Feature	Casio F-91W	Seiko Prospex 62MAS Modern Re-interpretation
Price	Under $50	$1,000–$1,500
Case Size	35mm	40.5mm
Movement	Quartz Module 593	Automatic 6R35
Caliber Type	Casio Digital Quartz (Battery)	Seiko In-House Automatic
Power Reserve	7-Year Battery	70 Hours
Water Resistance	30m (Splash Resistant)	200m (20 ATM)
Crystal	Acrylic	Sapphire
Case Material	Resin	Stainless Steel with Super-Hard Coating
Origin	Casio (Japan)	Made in Japan

Category-by-Category Analysis

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Design & Aesthetics

Edge: Draw

Casio's design language vs Seiko's approach

The Casio F-91W features a Resin case at 35mm with Acrylic protection. The Seiko Prospex 62MAS Modern Re-interpretation offers Stainless Steel with Super-Hard Coating construction at 40.5mm with Sapphire. Both represent their brand's distinct design philosophy and heritage.

⚙️

Movement & Performance

Edge: Seiko

Quartz Module 593 vs Automatic 6R35

The F-91W runs the Quartz Module 593 (Casio Digital Quartz (Battery), 7-Year Battery power reserve) at standard frequency. The Prospex 62MAS Modern Re-interpretation uses the Automatic 6R35 (Seiko In-House Automatic, 70 Hours reserve) at 21,600 vph (3 Hz). The Prospex 62MAS Modern Re-interpretation offers a longer power reserve.

📏

Wearability & Fit

Edge: Casio

35mm vs 40.5mm — different wrist presence

At 35mm, the F-91W wears more compactly on smaller wrists compared to the Prospex 62MAS Modern Re-interpretation at 40.5mm. Water resistance differs: 30m (Splash Resistant) vs 200m (20 ATM).

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Value & Cost of Ownership

Edge: Casio

Casio sits in the lower tier

The Casio F-91W sits at Under $50 and the Seiko Prospex 62MAS Modern Re-interpretation at $1,000–$1,500. On the specs that outlast any price: the F-91W uses Acrylic with 7-Year Battery, against Sapphire and 70 Hours on the Prospex 62MAS Modern Re-interpretation. Service intervals are typically 5-7 years for both.

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Water Resistance

Edge: Seiko

30m (Splash Resistant) vs 200m (20 ATM)

The F-91W is rated to 30m (Splash Resistant) while the Prospex 62MAS Modern Re-interpretation handles 200m (20 ATM). The Prospex 62MAS Modern Re-interpretation 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.

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Seiko

Prospex 62MAS Modern Re-interpretation

Choose the Seiko Prospex 62MAS Modern Re-interpretation if you value Seiko In-House Automatic technology, Made in Japan heritage, and 40.5mm proportions. At $1,000–$1,500, the Automatic 6R35 with 70 Hours power reserve makes it a compelling choice.

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The Bottom Line

The Casio F-91W and Seiko Prospex 62MAS Modern Re-interpretation represent two distinct approaches to fine watchmaking — the Casio bringing Casio (Japan) tradition while Seiko delivers Made in Japan engineering.

Frequently Asked Questions

The Seiko Prospex 62MAS Modern Re-interpretation is the better buy if you want a mechanical movement; the Casio F-91W is the better buy if you want quartz accuracy with no servicing. For water, the Seiko Prospex 62MAS Modern Re-interpretation is rated 200 m against 30 m, which is the difference between swimming and diving on one side and splashes on the other. On price, the Casio F-91W sits a band lower (Under $50 against $1,000–$1,500), so it is the cheaper way into the category. Neither is better at everything; the spec table above shows movement, case size, water resistance and crystal side by side so you can weigh what matters to you. We do not test units, so this is the makers' data, not a bench result.

The Casio F-91W offers better upfront value, sitting a tier lower at Under $50. However, the Seiko Prospex 62MAS Modern Re-interpretation may justify its premium with superior finishing, heritage, or resale value.

Both are suitable for daily wear. The F-91W at 35mm with 30m (Splash Resistant) water resistance handles everyday situations. The Prospex 62MAS Modern Re-interpretation at 40.5mm with 200m (20 ATM) is similarly capable. The F-91W uses Acrylic while the Prospex 62MAS Modern Re-interpretation uses Sapphire. Sapphire resists scratches noticeably better than acrylic.

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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.