Head-to-Head Comparison

Updated September 5, 2026

Seiko Presage SSA425 Open Heart vs Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue)

Two timepieces compared — $250–$500 vs $25,000+

Quick Verdict

The Seiko Presage SSA425 Open Heart ($250–$500) offers Seiko In-House Automatic precision in the tier below the Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) ($25,000+). The Presage SSA425 Open Heart measures 40.5mm and is rated 50m (5 ATM). The Executive Skeleton X 42mm (18k rose gold, blue) counters with Swiss Made craftsmanship and 100m (10 ATM) water resistance. Both are exceptional timepieces for their respective tiers.

SeikoPresage SSA425 Open Heart$250–$500 Check price Ulysse NardinExecutive Skeleton X 42mm (18k rose gold, blue)$25,000+ Check price

Transparency — We earn a small commission on purchases made through our Amazon links. This doesn't affect our editorial independence.

Seiko

Presage SSA425 Open Heart

$250–$500

Check Price Full Review

Ulysse Nardin

Executive Skeleton X 42mm (18k rose gold, blue)

$25,000+

Check Price Full Review

Specifications Compared

Feature	Seiko Presage SSA425 Open Heart	Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue)
Price	$250–$500	$25,000+
Case Size	40.5mm	42mm
Movement	Automatic Caliber 4R38	Hand-wound, Ulysse Nardin UN-371 (skeleton)
Caliber Type	Seiko In-House Automatic	UN-371, hand-wound, silicon escapement and balance spring
Power Reserve	41 Hours	About 96 hours (four days)
Water Resistance	50m (5 ATM)	100m (10 ATM)
Crystal	Hardlex Crystal	Sapphire Crystal, sapphire caseback
Case Material	Stainless Steel	18k rose gold, blue bezel
Origin	Made in Japan	Swiss Made

Category-by-Category Analysis

🎨

Design & Aesthetics

Edge: Draw

Seiko's design language vs Ulysse Nardin's approach

The Seiko Presage SSA425 Open Heart features a Stainless Steel case at 40.5mm with Hardlex Crystal protection. The Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) offers 18k rose gold, blue bezel construction at 42mm with Sapphire Crystal, sapphire caseback. Both represent their brand's distinct design philosophy and heritage.

⚙️

Movement & Performance

Edge: Ulysse Nardin

Automatic Caliber 4R38 vs Hand-wound, Ulysse Nardin UN-371 (skeleton)

The Presage SSA425 Open Heart runs the Automatic Caliber 4R38 (Seiko In-House Automatic, 41 Hours power reserve) at 21,600 vph (3 Hz) frequency. The Executive Skeleton X 42mm (18k rose gold, blue) uses the Hand-wound, Ulysse Nardin UN-371 (skeleton) (UN-371, hand-wound, silicon escapement and balance spring, About 96 hours (four days) reserve) at standard. The Executive Skeleton X 42mm (18k rose gold, blue) offers a longer power reserve.

📏

Wearability & Fit

Edge: Seiko

40.5mm vs 42mm — different wrist presence

At 40.5mm, the Presage SSA425 Open Heart wears more compactly on smaller wrists compared to the Executive Skeleton X 42mm (18k rose gold, blue) at 42mm. Water resistance differs: 50m (5 ATM) vs 100m (10 ATM).

💰

Value & Cost of Ownership

Edge: Seiko

Seiko sits in the lower tier

The Seiko Presage SSA425 Open Heart sits at $250–$500 and the Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) at $25,000+. On the specs that outlast any price: the Presage SSA425 Open Heart uses Hardlex Crystal with 41 Hours, against Sapphire Crystal, sapphire caseback and About 96 hours (four days) on the Executive Skeleton X 42mm (18k rose gold, blue). Service intervals are typically 5-7 years for both.

💧

Water Resistance

Edge: Ulysse Nardin

50m (5 ATM) vs 100m (10 ATM)

The Presage SSA425 Open Heart is rated to 50m (5 ATM) while the Executive Skeleton X 42mm (18k rose gold, blue) handles 100m (10 ATM). The Executive Skeleton X 42mm (18k rose gold, blue) offers superior water resistance.

Our Verdict

Seiko

Presage SSA425 Open Heart

Choose the Seiko Presage SSA425 Open Heart if you prioritize Seiko In-House Automatic engineering, Made in Japan craftsmanship, and 50m (5 ATM) water resistance. At $250–$500, it delivers Automatic Caliber 4R38 with 41 Hours power reserve.

Check Price on Amazon

Ulysse Nardin

Executive Skeleton X 42mm (18k rose gold, blue)

Choose the Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) if you value UN-371, hand-wound, silicon escapement and balance spring technology, Swiss Made heritage, and 42mm proportions. At $25,000+, the Hand-wound, Ulysse Nardin UN-371 (skeleton) with About 96 hours (four days) power reserve makes it a compelling choice.

Check Price on Amazon

Try Prime Free — Free Shipping on Both Watches Students & 18–24: start Prime for Young Adults free

The Bottom Line

The Seiko Presage SSA425 Open Heart and Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) represent two distinct approaches to the timepiece category — the Seiko bringing Made in Japan tradition while Ulysse Nardin delivers Swiss Made engineering.

Frequently Asked Questions

For water, the Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) is rated 100 m against 50 m, which is the difference between swimming and diving on one side and splashes on the other. On price, the Seiko Presage SSA425 Open Heart sits a band lower ($250–$500 against $25,000+), 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 Seiko Presage SSA425 Open Heart offers better upfront value, sitting a tier lower at $250–$500. However, the Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) may justify its premium with superior finishing, heritage, or resale value.

Both are suitable for daily wear. The Presage SSA425 Open Heart at 40.5mm with 50m (5 ATM) water resistance handles everyday situations. The Executive Skeleton X 42mm (18k rose gold, blue) at 42mm with 100m (10 ATM) is similarly capable. The Presage SSA425 Open Heart uses Hardlex Crystal while the Executive Skeleton X 42mm (18k rose gold, blue) uses Sapphire Crystal, sapphire caseback.

More Comparisons

Tag Heuer Carrera Chronograph vs Seiko Presage SSA425 Open Heart

Tag Heuer's chronograph meets Seiko's timepiece

Tag Heuer Carrera Chronograph vs Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue)

Tag Heuer's chronograph meets Ulysse Nardin's timepiece

Tissot PRX Powermatic 80 vs Seiko Presage SSA425 Open Heart

Two timepieces compared — $500–$1,000 vs $250–$500

Explore These Watches

Seiko Presage SSA425 Open Heart — Full Review Ulysse Nardin Executive Skeleton X 42mm (18k rose gold, blue) — Full Review Browse All Guides

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.