The most common first question for new Seiko modders isn't about dials or cases: it's which movement to use. The NH35 and NH36 are nearly identical, but the difference matters once you're choosing a dial. Use the Assemble Watches Seiko mod builder to visualise either movement in your build before committing.
Quick Comparison
| Feature | NH35 | NH36 |
|---|---|---|
| Complication | Date only | Day + date |
| Movement height | 5.32 mm | 5.32 mm |
| Outside diameter | 27.40 mm | 27.40 mm |
| Casing diameter | 29.36 mm with dial spacer | 29.36 mm with dial spacer |
| Frequency | 21,600 vph | 21,600 vph |
| Power reserve | ~41 hours | ~41 hours |
| Hacking / hand-wind | Yes / Yes | Yes / Yes |
| Jewels | 24 | 24 |
| Dial feet | Standard Seiko | Standard Seiko |
| Typical price | £20–£35 / $20–$35 | £30–£45 / $30–$45 |
When to Choose the NH35
The NH35 is the right choice for most first builds. It uses the same published height and footprint as the NH36, so the decision usually comes down to the dial. The NH35's date-only display means a wider selection of compatible dials: most aftermarket dials are cut for the NH35, and date-only apertures tend to look cleaner because they are smaller and less visually dominant.
Cost is a minor but real advantage too. The NH35 typically runs £10–£15 less than the NH36, which adds up if you're planning multiple builds or experimenting with different parts combinations before committing.
In practical terms: if you don't have a strong preference for seeing the day of the week on your watch, or if your dial of choice is NH35-cut, the NH35 is the safer default.
When to Choose the NH36
The NH36 makes sense when the day display is something you'll actually use. It's a small thing, but if you wear a watch as your primary time-telling device and you find yourself glancing at the day window regularly, the NH36 earns its slight premium. It's also the more common choice for field-watch-style builds, where the fuller date and day complication fits the utilitarian aesthetic.
Case fit is usually the same for both movements because TMI lists the same outside diameter, casing diameter, and total height for the NH35A and NH36A. Where you still need to check carefully is the dial and date window: an NH36 needs a day-date aperture, while an NH35 only needs a date aperture.
One practical note: the NH36's day wheel often defaults to English, but the wheel itself is interchangeable. Alternative language day wheels are available separately if you want something different.
What About the NH70 and NH71?
The NH70 and NH71 are worth knowing about if you're planning a no-date build. Both share the same footprint as the NH35 and NH36, so they drop into the same cases and accept the same hands.
The NH70, NH71, and NH72 are skeleton movements based around the same NH family architecture. They have no date or day display, use three hands, run at 21,600 bph, and include stop seconds. The practical difference is mostly finish: NH70 is the silver option, NH71 is gilt, and NH72 is a darker grey finish. They are useful when the movement is meant to be seen through the dial, not hidden behind it.
Which Movement Does Assemble Watches Support?
The Assemble Watches builder supports both the NH35 and NH36. Select your movement at the start of the build flow and the builder will filter compatible dials, cases, and hands automatically, including flagging dial aperture mismatches between NH35-cut and NH36-cut dials.
Frequently Asked Questions
Is the NH35 or NH36 more reliable?
Both are equally reliable. They share the same movement architecture, frequency, power reserve, and jewel count. Reliability differences between individual units are normal manufacturing variance, not a fundamental difference between the two calibres.
Can I use an NH36 in a case designed for an NH35?
Usually yes. TMI lists the NH35A and NH36A with the same outside diameter, casing diameter, and 5.32mm total height. The part you need to check is normally the dial: an NH36 needs a day-date aperture, while an NH35 only needs a date aperture.
Where can I see which movements are compatible with my chosen case?
Use the Assemble Watches builder. Select the case you're interested in and the builder will show which movements fit it, along with compatible dials and hands.
What's the price difference between NH35 and NH36?
The NH36 typically costs £10–£15 more than the NH35 from the same vendor. On current pricing this means roughly £30–£35 for the NH35 versus £40–£45 for the NH36. Prices vary by vendor and region.