Quick answer: The Seiko NH70A is a factory-skeletonised automatic watch movement made by Seiko (TMI). It has 24 jewels, beats at 21,600 vibrations per hour, offers about 41 hours of power reserve, and supports hacking seconds and hand-winding. It has no date. It is essentially the skeletonised version of the Seiko NH38, which makes it one of the most reliable and affordable ways to build a genuine skeleton watch.
Seiko NH70A Specifications
| Specification | NH70A |
|---|---|
| Type | Automatic, self-winding, skeletonised |
| Maker | Seiko Instruments / TMI |
| Jewels | 24 |
| Beat rate | 21,600 vph (6 beats per second) |
| Power reserve | About 41 hours |
| Hand-winding | Yes |
| Hacking seconds | Yes (seconds hand stops when setting time) |
| Date | No |
| Official accuracy tolerance | About −35 to +45 seconds per day (NH-series spec); most run well inside this |
NH70 vs NH70A: Is There a Difference?
No. NH70 and NH70A refer to the same calibre. The "A" is part of the movement's full reference code, and watchmakers, brands and parts suppliers use the two names interchangeably. If a watch lists either one, you are getting the same 24-jewel skeletonised automatic.
NH70 vs NH35 vs NH38
| Movement | Date | Skeletonised | Best for |
|---|---|---|---|
| NH35 | Yes | No | Dive and field watches with a date |
| NH38 | No | No | Clean no-date dials, often with exhibition casebacks |
| NH70 | No | Yes | Skeleton watches, visible from front and back |
All three share the same core architecture, so parts and servicing are widely available. That shared base is why the NH70 has become the go-to movement for accessible skeleton watches.
What 21,600 vph Means on Your Wrist
21,600 vibrations per hour means the balance wheel ticks six times every second. On a skeleton dial you can see this directly: the balance wheel oscillates steadily while the seconds hand moves in six small steps per second, giving the smooth sweep associated with mechanical watches rather than the one-step-per-second jump of a quartz watch.
How Accurate Is the NH70A?
Seiko's published tolerance is generous because it covers every movement in every position. In real daily wear, most NH-series movements run within roughly 10 to 20 seconds per day, and a watchmaker can regulate them tighter. That is normal for a mechanical automatic. If you need quartz-level precision, see automatic vs quartz watches.
How to Wind and Set an NH70A Watch
- Hand-wind: with the crown pushed in (position 0), turn it clockwise about 20 to 30 times to start a stopped watch.
- Set the time: pull the crown to position 1. The seconds hand stops (hacking), so you can set the time to the second.
- Wear it: daily wrist movement keeps the rotor winding the mainspring.
If you take the watch off, it keeps running for roughly a day and a half before it needs wearing or winding.
Why Does My NH70A Stop Overnight?
A fully wound NH70A runs for about 41 hours, but it only reaches full wind if the rotor gets enough movement. A few hours of desk work or light wear may only partly wind the mainspring, so the watch can stop overnight. The fix is simple: give the crown 20 to 30 clockwise turns in the morning, or wear the watch for a full day. This is normal behaviour for any automatic and not a fault.
Is Rotor Noise Normal?
Yes. On the NH-series the rotor spins freely in both directions and can make a soft whirring sound when you move your wrist quickly. Because a skeleton watch has an open dial and exhibition caseback, you may notice it more than on a closed watch. A grinding or scraping sound, or a rotor that visibly wobbles against the case, is different and worth having checked.
Servicing and Longevity
A well-kept NH70A can run for many years. A general service every 4 to 6 years keeps oils fresh and timing consistent. Avoid strong magnets (speakers, phone cases with magnetic clasps, tablet covers), which can make any mechanical watch run fast.
Signs it is time for a service:
- The watch gains or loses noticeably more time than it used to
- It stops well short of its usual power reserve after a full wind
- Hand-winding feels gritty or the crown feels rough
For day-to-day care in heat, humidity and sand, see our guide to watch maintenance for UAE conditions.
Why the NH70A Suits a Skeleton Watch
Because Seiko skeletonises the movement at the factory, you get an open, visible mechanism without the reliability risk of cutting away a standard movement by hand. The bridges are shaped for visibility, and the rotor and balance wheel are fully on show. New to the style? Start with what a skeleton watch is, then read our honest take on whether a skeleton watch is worth it.
Verso Parnell Skeleton Watches With the NH70A
Verso Parnell's skeleton watches pair this movement with an octagonal 316L stainless steel case, sapphire crystal, and an integrated bracelet:
- Nebula Sport Skeleton: AED 1,900 (approx. USD 517)
- Nebula Skeleton: AED 2,000 (approx. USD 545)
- Silverera Skeleton: AED 2,100 (approx. USD 572)
Each watch ships free worldwide in a handcrafted wooden box, with a 2-year international warranty and 30-day returns. These pieces are from the current production run of NH70A-powered models.
Frequently Asked Questions
Is the Seiko NH70 a good movement?
Yes. It is robust, widely serviceable, and one of the most reliable skeleton movements at its price.
Does the NH70 have a date?
No. It is a time-only movement: hours, minutes, and seconds.
What is the difference between the NH70 and NH38?
The NH70 is the skeletonised version of the NH38. Function and specs are essentially the same; the NH70 is opened up for visibility.
What is the power reserve of the NH70A?
About 41 hours when fully wound.
Can you hand-wind the NH70A?
Yes. Turn the crown clockwise in its pushed-in position.
Is the NH70 the same as the NH70A?
Yes. The two names refer to the same calibre and are used interchangeably.
Does the NH70A need a battery?
No. It is powered entirely by the mainspring, which is wound by the rotor as you move or by turning the crown.
How often should an NH70A be serviced?
Every 4 to 6 years is a sensible interval, or sooner if timekeeping or power reserve changes noticeably.
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