Reference
Seiko NH35 (NH35A) Movement — Reference & Specifications
What the NH35 is
The Seiko NH35 (full code NH35A) is an automatic mechanical watch movement built by Seiko Instruments Inc. (SII) and its watch-module arm Time Module Inc. (TMI). It winds automatically and by hand, hacks the seconds for precise time-setting, beats at 21,600 bph on 24 jewels, and stores roughly 41 hours of power. Mechanically it is the unbranded twin of Seiko's in-house 4R35 caliber — the reason it turns up in Seiko 5 watches and, above all, across the microbrand and modification world. This page is a reference record, not a modding how-to.
NH35 specifications
| Spec | Value |
|---|---|
| Model code | NH35 / NH35A |
| Manufacturer | Seiko Instruments (SII) / Time Module (TMI) |
| Type | Automatic, mechanical |
| Winding | Bi-directional automatic (Magic Lever) + manual hand-winding |
| Hacking seconds | Yes |
| Jewels | 24 |
| Frequency | 21,600 bph (3 Hz) |
| Power reserve | ~41 hours (factory spec "more than 41 h") |
| Factory accuracy | −20 to +40 sec/day |
| Diameter | 27.4 mm (12''') |
| Height | 5.32 mm |
| Lift angle | 53° |
| Complications | Date, quick-set (date only) |
| Shock protection | Seiko Diashock |
| Introduced | 2011 |
Manual winding takes roughly 55 crown turns (clockwise) to go from fully run-down to fully wound. The −20/+40 figure is Seiko's outer factory tolerance; individual movements often run tighter and can be regulated.
NH35 vs 4R35 vs NH36
The NH-series and 4R-series are the same movements under two names: 4R calibers go into Seiko's own branded watches, while NH calibers are the versions SII/TMI sells to third parties.
| Caliber | Branding | Complications | Jewels | Notes |
|---|---|---|---|---|
| NH35 | Third-party (SII/TMI) | Date | 24 | Unbranded twin of the 4R35 |
| 4R35 | Seiko in-house | Date | 24 | Same movement, Seiko-branded |
| NH36 | Third-party (SII/TMI) | Day + Date | 24 | Adds a day wheel; equivalent to 4R36 |
Because the NH35 and NH36 share the same base architecture and dimensions, a case or dial built for one physically accepts the other — the practical difference is only whether you want a day complication.
Watches that use the NH35
The NH35 powers a wide field of affordable automatics beyond Seiko's own line, including microbrands and OEM builders. Reference sources list users such as Invicta, Vostok, Lum-Tec, Spinnaker, Boldr, Audaz, and Pagani Design, alongside countless smaller labels. Inside Seiko's catalog, the closely related 4R35 and day-date 4R36 appear across the modern Seiko 5 family and SRPD/SSK cases.
Why it anchors the mod scene
The NH35 became the default "heart" of Seiko-style modding because it is inexpensive, widely stocked as a loose movement, and dimensionally matched to popular SKX/SRPD-style cases, dials, and hands. It hacks and hand-winds (features the older 7S26 lacked), uses a Diashock-protected Glucydur balance, and swaps in and out without special tooling. That combination of low cost, availability, and parts compatibility is what makes it the standard base for entry-level automatic builds.
Sources
FAQ
- Is the Seiko NH35 the same as the 4R35?
- Effectively yes. The NH35 and 4R35 share the same architecture and specifications; the difference is distribution. Seiko Instruments/TMI sells the unbranded NH35 to microbrands and modders, while the 4R35 designation is used in Seiko's own watches. Both are date-only automatics with hacking and hand-winding.
- Does the NH35 hack and hand-wind?
- Yes to both. Pulling the crown stops (hacks) the seconds hand for precise time-setting, and the crown also winds the mainspring manually — roughly 55 clockwise turns from fully run-down. These are the features that separated the NH-series from the older, non-hacking 7S26.
- How accurate is the NH35?
- Seiko's factory tolerance is -20 to +40 seconds per day, an intentionally wide band for an affordable movement. Many individual movements run well inside that range, and a watchmaker can regulate an NH35 tighter. Reference sources cite the same -20/+40 spec; real-world results vary per unit.
This article is for information only and is not investment, valuation, or authentication advice. Prices, availability and release dates change — always confirm with the retailer or official source linked in the article before buying.