NH72 Skeleton Automatic Movement
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The Seiko NH72 is the most popular skeleton movement in the Seiko modding world. Manufactured by TMI (Time Module Inc.), a subsidiary of Seiko Instruments, the NH72 features open-worked bridges finished in a dark plating that creates striking contrast when viewed through a skeleton dial. The dark bridges against the metallic internal components produce a dramatic depth effect that neither the silver NH70 nor the gold NH71 can match. Same proven platform underneath: 21,600 bph, 24 jewels, 41-hour power reserve, hacking, and hand-winding.
Specifications
| Specification | Detail |
|---|---|
| Caliber | Seiko NH72A |
| Type | Automatic Skeleton |
| Frequency | 21,600 bph (6 beats per second) |
| Jewels | 24 |
| Power Reserve | 41 hours |
| Hacking | Yes |
| Hand-Winding | Yes |
| Date | No |
| Skeleton | Yes (open-worked bridges) |
| Bridge Finish | Dark-plated (black) |
| Stem Position | 3 o’clock |
| Rotor | Bidirectional |
Compatibility
The NH72 fits every Nomods case: Royal Oak 37 mm, Royal Oak 41 mm, Petrichor, and Seikonaut. As with all skeleton movements, it requires a skeleton dial to show the dark-plated open-worked bridges. The NH72’s dark finish pairs naturally with silver, gunmetal, and black cases where the dark bridges create visual depth through the dial cutouts. It also works well with rose gold cases for a contrasting warm-cool combination.
Dial sizes: 28.5 mm skeleton dials for the Royal Oak 37 mm and Petrichor cases · 30.8 mm skeleton dials for the Royal Oak 41 mm and Seikonaut cases
Hands: All Nomods hands are compatible with the NH72 skeleton movement. Crown sits at 3 o’clock.
What’s Included
- Seiko NH72A skeleton movement (fully assembled with rotor)
- Stem
- Movement specification sheet
Why This Movement
The NH72 is the skeleton movement that most Seiko mod builders choose, and for good reason. The dark-plated bridges create a level of visual contrast that the silver NH70 and gold NH71 cannot replicate. When viewed through a skeleton dial, the dark bridges frame the bright metallic gears, jewels, and balance wheel in a way that draws the eye into the movement rather than reflecting light off the surface. This depth effect is what makes the NH72 the defining movement for open heart and skeleton Seiko builds. Nomods uses the NH72 as the default skeleton caliber in its Royal Oak Skeleton, Seikonaut Skeleton, and Petrichor Skeleton configurations.
Frequently Asked Questions
What is the difference between the NH72 and NH70?
The NH72 and NH70 are mechanically identical skeleton movements — same 21,600 bph frequency, 24 jewels, 41-hour power reserve, hacking, and hand-winding. The difference is the bridge finish: the NH72 has dark-plated (black) bridges that create dramatic contrast through a skeleton dial, while the NH70 has natural silver bridges for a cleaner, more industrial look. The NH72 is the more popular choice because the dark bridges produce a stronger visual depth effect.
Does the NH72 require a skeleton dial?
Yes, a skeleton dial is essential to see the dark-plated open-worked bridges. Skeleton dials have cutouts or transparent sections that reveal the movement underneath. Installing a solid dial would completely hide the NH72’s signature dark bridge finish, and you would be better served by the less expensive NH38 (no-date, solid bridges) since the skeleton decoration would be invisible.
How accurate is the NH72 skeleton movement?
The factory specification is ±20 seconds per day, identical to the NH35, NH70, and NH71. The dark plating and open-worked bridges are cosmetic treatments only and do not affect the movement’s timekeeping performance. A watchmaker can regulate the NH72 for improved accuracy if desired.
Complete Your Build
- Nautilus Skeleton Dial (30.8 mm, Silver) — the dark NH72 bridges contrast beautifully against silver skeleton dials
- Royal Oak 37 mm Case (Silver) — silver case with skeleton dial cutouts for the NH72
- Seikonaut Nautilus Case — nautilus-style case for 30.8 mm skeleton dials
- Hands — all Nomods hands are compatible with the NH72
- NH72 Skeleton Movement Guide — comprehensive guide to building with the NH72
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