Underdial
The NH35 and NH38 are virtually identical Seiko automatic movements, same architecture, same power reserve, same accuracy. The only meaningful difference: the NH35 includes a date complication; the NH38 doesn't. Choose NH38 for a cleaner, symmetrical dial. Choose NH35 if you want a date window.
When you’re shopping microbrand watches or planning a Seiko mod, you’ll hit the NH35 and NH38 almost immediately. They look nearly identical on a spec sheet, most guides treat them as interchangeable, and the name difference suggests something significant must separate them. It doesn’t. Knowing exactly what does differ saves you from making the wrong call before you spend.
A question we hear often: buyers assume the number gap implies a meaningful upgrade. It doesn’t.
In plain terms, the NH38 is the NH35 with the date complication removed. That single difference is the whole reason it exists, and it’s why it has become a quiet favourite among buyers and modders who want an uninterrupted, symmetrical dial. Everything else, including the movement architecture, the oscillation frequency, the power reserve, and the winding and hacking behaviour, is shared between them.
Seiko Instruments Inc. (SII) built the NH series for external supply in the early 2010s. Mechanically, these calibres mirror their in-house 4R counterparts: the NH35 shares its base architecture with the 4R35, and the NH38 follows the same pattern.
All NH movements support automatic winding via a rotor and manual winding via the crown. The seconds hand stops when you set the time (hacking seconds), allowing precise synchronisation. Power reserve runs approximately 41 hours, and frequency sits at 21,600 beats per hour, or 3Hz.
A common assumption is that the NH38 offers higher accuracy than its siblings. It doesn’t. The NH38 runs to the same Seiko tolerance as the NH35, so choosing it is about dial layout, not precision. Both movements are rated at roughly ±15 seconds per day under normal conditions. That’s consistent with what you’d expect from a well-made Japanese automatic at this price tier, and it’s honest: a COSC-certified Swiss movement it is not, but a dependable daily driver it absolutely is.
If accuracy is your primary concern, neither movement wins over the other. You’d need to look at something like the Miyota 9015 or the Sellita SW200, which we cover in our NH35 vs Miyota 9015 comparison.
This one comes up a lot: especially from buyers shortlisting two microbrands where one specs the NH35 and the other the NH38.
Every NH shares one architecture, Seiko’s Type M, so dials, hands, and cases move freely between them. What changes is the complication and, on certain variants, the finish. The core rule: reach for the movement your dial is cut for. A date dial needs the NH35; a day-date needs the NH36; an open-heart or sterile (no-date) dial suits the NH38; a GMT layout needs the NH34.
In practice, look at the dial first. If the watch has a date window at 3 o’clock (or 4, or 6), it’s almost certainly NH35-powered, and that’s fine. If the dial is clean and symmetrical with no window or interruption, expect the NH38. Because the NH38 drops the date complication entirely, it’s a natural fit for open-heart displays, where the escapement is visible through the dial and any asymmetry would be immediately obvious.
One practical detail that rarely gets mentioned: there’s a “ghost” crown position on any no-date watch running an NH35. That third stop, the date-set position, sits there doing nothing. It’s a minor annoyance, but once you notice it, you keep noticing it. The NH38 removes it, leaving a clean two-position crown that matches what the dial is actually doing.
| Feature | NH35 | NH38 |
|---|---|---|
| Made by | Seiko Instruments Inc. (SII) | Seiko Instruments Inc. (SII) |
| Base architecture | 4R35 / Type M | 4R35 / Type M |
| Frequency | 21,600 bph (3 Hz) | 21,600 bph (3 Hz) |
| Power reserve | ~41 hours | ~41 hours |
| Jewel count | 24 | 24 |
| Hacking seconds | Yes | Yes |
| Hand-winding | Yes | Yes |
| Date complication | Yes (3 o’clock) | No |
| Crown positions | 3 (wind / set time / set date) | 2 (wind / set time) |
| Open-heart compatible | No | Yes |
| Typical accuracy | ±15 s/day | ±15 s/day |
| Serviceability | Widely available globally | Widely available globally |
| Wholesale cost | Slightly lower | Slightly higher |
Readers frequently ask: whether the NH38 carries a premium and whether it’s worth paying.
At the wholesale level, the NH38 costs fractionally more than the NH35. The gap is small enough that it rarely drives meaningful price differences in finished watches on its own. What actually tends to cost more is the context the NH38 lives in. Brands that specify a no-date movement typically care more about dial symmetry and overall finishing, so the watches they produce are often positioned at a slightly higher tier regardless of movement cost. You’re paying for design intent as much as the calibre itself.
That said, you won’t find a dramatic price cliff between two otherwise comparable watches where the only difference is NH35 vs NH38. If a microbrand is charging $150 more for the NH38 version of an otherwise identical watch, that delta is probably explained by dial quality, case finishing, crystal choice, or bracelet, not the movement. Run both candidates through Underdial’s spec checker to confirm what you’re actually getting for the extra money before committing.
Swapping between them is possible in principle, but you need to account for more than just the movement itself. Every NH shares one architecture, so dials, hands, and cases move freely between them, provided the dial is cut to match. A no-date dial fitted over an NH35 will work, but you’ll have that ghost third crown position. A date dial over an NH38 leaves a blank hole in the dial with no wheel behind it to display anything, which is a non-starter.
The cleanest approach: decide date or no-date first, then choose the movement. The modding community’s general consensus, echoed across forum threads, is that the NH38 produces the most refined-looking builds precisely because the crown geometry and dial design are aligned from the start. For first-time builders who want flexibility later, some opt for the NH35 even with a no-date dial, knowing they can swap to a date dial down the road without replacing the movement.
From a serviceability standpoint, both calibres are about as friendly as affordable automatics get. Replacement NH35 movements are inexpensive and widely stocked, and fitting one is a routine job. The same holds for the NH38. Any watchmaker with experience on the broader NH/4R family, which covers the vast majority of technicians who work on affordable automatics, can handle either calibre without specialist tools or unusual parts.
Compared to a proprietary movement from a lesser-known brand, this matters enormously for long-term ownership. An NH-powered watch bought today can realistically be kept running for decades, not just until the brand stops stocking spares.
Is the NH38 more accurate than the NH35? No. Both movements share the same Seiko tolerance of approximately ±15 seconds per day and run at 21,600 bph. Choosing between them is a dial-layout decision, not a precision one.
Can I use a no-date dial with an NH35? Yes. You can fit a no-date dial on an NH35, but you’ll have an unused crown position (the date-set position) that serves no function. The NH38 removes that ghost position entirely, giving you a two-position crown.
Is the NH38 harder to service than the NH35? No. Both share the same base architecture and are widely stocked by watchmakers worldwide. Any technician familiar with the NH35 can service an NH38 without extra training or unusual parts.
Why do some microbrands charge more for NH38 watches? The NH38 costs slightly more than the NH35 at the wholesale level. Beyond that, brands that specify the NH38 typically target enthusiasts who value no-date aesthetics, so they tend to invest more in dial and case finishing overall, which raises the total price above what the movement alone justifies.
What’s the difference between the NH38 and the NH34? The NH34 is the GMT version, with an independently settable 24-hour hand for tracking a second time zone. The NH38 drops the date and leaves a clean, open balance instead. The base movement is the same across all of them, but the NH34 serves a completely different purpose, while the NH38 is simply a no-frills automatic.
Should I buy a watch with an NH35 or NH38 as my first automatic? Either is a solid foundation. If you want the practicality of a date display, lean NH35. If you’re drawn to symmetrical dials and cleaner aesthetics, the NH38 delivers the same dependable movement in a more considered package. Either way, the watch around the movement, its case, dial, and crystal, will matter far more to your daily enjoyment than which of these two sibling calibres sits inside it.
Is the NH38 more accurate than the NH35?
No. Both movements share the same Seiko tolerance of approximately ±15 seconds per day and run at 21,600 bph. Choosing between them is a dial-layout decision, not a precision one.
Can I use a no-date dial with an NH35?
Yes, you can fit a no-date dial on an NH35, but you'll have an unused crown position (the date-set position) that serves no function. The NH38 removes that ghost position entirely, giving you a two-position crown.
Is the NH38 harder to service than the NH35?
No. Both share the same base architecture and are widely stocked by watchmakers worldwide. Any technician familiar with the NH35 can service an NH38 without extra training or parts.
Why do some microbrands charge more for NH38 watches?
The NH38 costs slightly more than the NH35 at the wholesale level. More importantly, brands that specify the NH38 typically target enthusiasts who appreciate no-date aesthetics, so they often invest more in dial and finishing quality overall, which raises the price.
What's the difference between the NH38 and the NH34?
The NH34 is the GMT member of the family, it adds an independently settable 24-hour hand for tracking a second time zone. The NH38 is a no-date automatic with no additional complications. They share the same base movement architecture but serve completely different purposes.