Custom Seikosub Edition Obsidian Black-OUT Open Heart MOD
$3206,013
40 mmSapphire
The Sensei's take
The CUSTOM SEIKOSUB EDITION OBSIDIAN BLACK-OUT is a striking choice for those seeking a blend of mechanical craftsmanship and modern aesthetics. Its open-heart design paired with a durable, stealthy look makes it a standout in any collection, offering exceptional value for watch enthusiasts who appreciate both style and substance.
Is this watch your kind of thing?
One vote per visitor — see how the community feels.
The Obsidian Black-Out Open Mod is a modern expression of stealth and precision, showcasing a partially open dial that reveals the intricate Seiko NH70 automatic movement. Its full black aesthetic, paired with a rotating bezel and sapphire crystal, delivers a powerful blend of sport and sophistication. Luminous markers ensure readability in all conditions, while the open-heart design highlights the watch’s mechanical character. Constructed from black PVD-coated 316L stainless steel and fitted with a durable rubber strap, it offers both comfort and resilience. The exhibition case back adds visual intrigue, completing a 40mm timepiece built for those who appreciate mechanical artistry and minimalist refinement. Specification Details Diameter 40 mm (excluding crown) Thickness 13 mm Movement S…
—
UnratedSensei Score — Unrated
Not yet scored by the Sensei.
Independent rating. Purchase links may be affiliate.
At a glance
Strengths & trade-offs
Pulled straight from the spec sheet, framed for the buyer. The editorial verdict is the Sensei's take above.
Strengths
- Scratch-resistant sapphire crystal
- Versatile 40mm case
- Luminous dial and hands
Trade-offs
- Priced above what the spec suggests
Sensei Says
The specs, in plain English
On the wrist
At 40 mm it lands in the modern sweet spot.
The value
Fairly priced for what it is.
On the wrist
How will this watch fit me?
Enter your wrist size once — we'll remember it — and the Sensei estimates the fit from the case measurements.
Wrist circumference
Preferred fit
Enter your wrist size to see the fit estimate.
Specifications
- Released
- 2025
- Case diameter
- 40 mm
- Thickness
- 13 mm
- Lug width
- 20 mm
- Case shape
- Round
- Case material
- Stainless Steel
- Crystal
- Sapphire
- Bezel
- Dive (unidirectional)
- Caseback
- Exhibition
- Dial colour
- black
- Dial finish
- Matte
- Indices
- luminous markers
- Lume
- Yes — luminous
- Strap / bracelet
- rubber
- Clasp
- buckle
- Functions
- Hours, Minutes, Seconds
- Fit
- Unisex
The maker
Monomods
Monomods positions itself against "watch hype" — pushing back on watches that look premium but hide what actually matters: overdesigned dials, inflated stories, and no clarity about what's inside or who stands behind it. Their stated response is transparency: using proven Japanese movements, transparent components, and careful assembly, with real support after purchase
Alternatives worth a look
Cheaper alternative
$40 less
Smaller alternative
2.0mm smaller
Better movement
Entry-level movement
More from Monomods
From the same maker
In the same spirit
Custom Seikosub Edition Obsidian Black-OUT Open Heart MOD vs Custom Gmteiko Edition Midnight Gold GMT MODCustom Seikosub Edition Obsidian Black-OUT Open Heart MOD vs Custom Royal Seikoak Edition Brushed Steel MODCustom Seikosub Edition Obsidian Black-OUT Open Heart MOD vs Custom Seidweller Edition Polar White MODCustom Seikosub Edition Obsidian Black-OUT Open Heart MOD vs Custom Seikoak Special Edition Blacked OUT Skeleton MOD