A short history of the NH family.

The Seiko NH-series didn't exist before 2011. In the fifteen years since, it has become the most-modded movement family in the world. Here's how a quiet OEM calibre took over an entire hobby.

Before the NH family — the 7S26

To understand the NH-series, you have to understand what it replaced. From 1996 until the mid-2010s, Seiko's affordable mechanical line was powered by the 7S26 — a workhorse automatic movement that lived inside the original Seiko 5, the SKX007 dive watch, the SKX013, and dozens of other models that defined affordable Japanese mechanical watchmaking.

The 7S26 was a great movement for its price (which was very low). It was also missing two features that watch enthusiasts considered minimum-stakes by the 2010s: it didn't have hacking seconds (you couldn't stop the second hand when setting the time), and it couldn't be hand-wound (you had to physically shake the watch to wake it from a dead reserve). Neither was a problem for casual wearers — these were entry-level mechanical watches and most owners never thought about either feature. But for modders building serious tool watches and Rolex homages, the 7S26 felt second-rate.

2011 — the NH35 arrives

In 2011, Seiko Instruments Inc. (the manufacturing arm) introduced a new family of movements: the NE15 (high-grade) and NH35 (entry-grade). The NH35 was specifically designed for OEM sales to third-party watchmakers — companies like Invicta and various microbrands who built their own watches around a bought-in Japanese movement.

The NH35 fixed the two big complaints about the 7S26. It hacked the seconds. It hand-wound through the crown. It also retained the 7S26's robustness, its 21,600 BPH frequency, and roughly its dimensions — meaning cases designed for the older movement could mostly accept the new one with minimal modification.

The price point was the killer feature. The NH35 wholesales to OEMs at roughly US$30–$40 per movement. For modders sourcing through the same channels, it was the cheapest hackable, hand-winding automatic on the market by a significant margin.

2014–2018 — the modders found it

The modding community took a few years to fully absorb what the NH35 meant. Through the mid-2010s, modding still revolved primarily around the 7S26 inside the SKX007 — partly because the SKX was still in production and partly because the aftermarket parts ecosystem was built around it.

What changed was supply. Seiko began making more cases and watches with NH35s rather than 7S26s. Modders following the new builds started using the NH35 as the base movement. The compatibility was easy because the dimensions were nearly identical. Within a few years, every major modding supplier was selling NH35-compatible dials, hands, and cases as standard.

By 2018, the modding community had largely shifted to the NH35 as the default movement. The SKX007 was officially discontinued in 2019, which closed the door on the 7S26 era for new builds. The NH35 was now the universal Seiko-modding standard.

The siblings emerge

Around the same time, Seiko expanded the NH family to cover specific market needs:

NH36 — day-date complication. Aimed at brands building Rolex Day-Date homages and similar dressy automatic watches.

NH38 — no date. Aimed at brands building clean-dial pilot watches and dress watches where the date complication would have been a design intrusion.

NH05 — slimmer, slightly smaller, often used in diver-style watches with bezels. Adopted heavily by Asian microbrands building Submariner-style and Datejust-style watches at affordable price points.

NH70 — fully skeletonised. Aimed at the growing market for transparent and exhibition-style watches at affordable prices. The Tissot PRX skeleton popularised this style; the NH70 made it accessible to modders at one-fifth the Swiss equivalent's price.

All five movements shared the same base architecture, the same 21,600 BPH frequency, the same 41-hour power reserve, and largely the same physical dimensions. The aftermarket could support all five with minor variations on the same parts.

Why this matters now

By 2025, the NH-series powered the majority of microbrand mechanical watches sold globally. The Indian-Singaporean watch market runs on it. The Australian microbrand scene runs on it. The Chinese watch modding community runs on it. The global Reddit-based modding community runs on it.

What Seiko Instruments built in 2011 as a competent OEM calibre has become — without much fanfare from Seiko itself — the most-used mechanical movement family in the world by unit volume that isn't a clone or a counterfeit. More NH35s are built every year than any other Swiss-style automatic movement.

"What Seiko built as a competent OEM calibre has become the most-used Swiss-style automatic movement family in the world."

The Magic Lever

One of the NH family's quietly distinctive features is the winding mechanism. Most automatic watches use a "switching rocker" or similar reversing mechanism that lets the rotor wind the mainspring regardless of which direction it's swinging. The NH-series uses Seiko's proprietary Magic Lever — a simpler design where a single sprung lever pulls the winding wheel in one direction only.

This is mechanically simpler (fewer parts, less to wear out) but slightly less efficient (the rotor only winds in one direction; it freewheels in the other). In practice, on a wrist, the lost efficiency doesn't matter — the rotor swings enough in both directions across the day to keep the mainspring topped up.

The Magic Lever was invented by Seiko in 1959 for the King Seiko and Grand Seiko of the era. It's been carried forward through every Seiko automatic since, including the entire NH family. When you wind an NH35 by hand or watch the rotor spin behind a display caseback, you're interacting with a 65-year-old piece of mechanical design that Seiko quietly perfected.

The criticisms

The NH-series isn't universally loved. Within the broader watch community, it has critics. The most common complaints:

"It's not finished enough." The visible parts of an NH35 — the rotor, the bridges — are industrially decorated rather than hand-finished. Compared to a similarly-priced Swiss ETA 2824-2, the NH35 looks more like a tool than an heirloom. This is a fair criticism if your priority is visual refinement. It's mostly irrelevant if your priority is a working watch behind a solid caseback.

"Accuracy is only middling." Factory-tolerance NH35s can run as far off as +40 to -20 seconds per day. The Swiss equivalent is tighter. This is also fair, but it's worth noting that a regulated NH35 settles within ±5 seconds per day — the factory tolerance is the spec, not the achievable accuracy.

"The Magic Lever is less efficient." Technically true; practically irrelevant for a daily-worn watch. The rotor winds enough in everyday wear.

None of these complaints change the calibre's positioning. The NH-series isn't trying to be a Patek movement. It's trying to be a reliable, affordable, modular automatic that puts mechanical watchmaking in reach of anyone who wants it. It does that better than anything else on the market.

What's next

Seiko hasn't announced a successor to the NH family, but they don't typically pre-announce. The NE15 (a higher-grade cousin used in the more expensive Seiko 5 Sports range) and the NE88 (column-wheel chronograph) suggest the family is still being expanded upward rather than replaced.

What's more interesting is that as Swatch Group has restricted ETA sales to outsiders, the NH-series has effectively become the only widely-available, mass-produced automatic mechanical movement in the world. Every microbrand that would have used an ETA a decade ago now uses an NH35 — or builds their own movement at significantly higher cost. The Japanese supply chain runs the entire affordable-mechanical sector.

Whether Seiko intended this or not, the NH35 has become a strategic component in global watchmaking. The 2011 OEM movement quietly took over the world.