This is one of the most searched Seiko movement questions, and it starts from a mismatch. The 4R36 is a day-date movement. The NH35 is date only. They are not counterparts, and comparing them is like comparing a car to the same car without rear doors.
The Pairings That Actually Match
- 4R35 equals NH35. Date only.
- 4R36 equals NH36. Day and date.
So if you are weighing up a Seiko against a microbrand and want a like-for-like answer, the comparison you want is 4R36 against NH36. Within each pair the movements are the same object with a different name stamped on it.
Why There Are Two Names at All
Both come out of Seiko. Seiko Instruments produces the 4R calibres for Seiko-branded watches. Time Module Inc, a Seiko subsidiary, sells the mechanically identical NH versions to third-party brands, microbrands and modders. Same architecture, same parts, different distribution channel.
That is genuinely the whole difference. Balance wheel, hairspring, pallet fork, escape wheel and mainspring are the same components.
The Specification Puzzle, and Its Answer
Here is the oddity that trips people up. Seiko publishes the 4R35 and 4R36 at roughly -35 to +45 seconds per day. Time Module publishes the identical NH35 and NH36 at a tighter -20 to +40. Same movement, better number.
The explanation is in the test conditions, not the hardware. Time Module’s technical documentation records those measurements with the date complication inactive. Different test setup, different published figure, identical watch on your wrist.
Which is a useful lesson well beyond Seiko: published movement tolerances describe a test protocol as much as they describe a movement.
Shared Specifications
- 24 jewels
- 21,600 vibrations per hour
- Power reserve of more than 41 hours
- 27.40mm diameter
- Hacking seconds and hand-winding, neither of which the older 7S26 had
- Lift angle of 53 degrees for timing purposes
Choosing Between Date and Day-Date
If you are actually deciding rather than just identifying, the question is only whether you want the day of the week.
The day-date versions have four crown positions rather than three, adding a quickset day. They also sit slightly thicker and cost a little more as bare movements. And the dial has to match: a day-date movement needs a dial with both windows cut for it.
Which One Is in My Watch?
Simple rule. If the watch says Seiko on the dial, it has a 4R. If it is a microbrand, a homage or a modded build, it has an NH. There is no version where a Seiko-branded watch contains an NH-stamped movement, because Seiko reserves the 4R designation for its own watches.
The Upgrade Path From a 7S26
Worth knowing if you own an older Seiko 5 or SKX. The 7S26’s day and date wheels and movement spacers are interchangeable with the 4R36 and NH36. That means a worn 7S26 can be replaced with an NH36 without hunting for new wheels, and you gain hacking and hand-winding in the process.
Given that a full service on a 7S26 often costs more than a replacement movement, this is frequently the more sensible repair on a low-value watch.
Conclusion
The 4R36 and NH35 are not rivals and never were. The 4R36’s counterpart is the NH36, and within that pair the only real difference is which brand is allowed to put it in a watch. Ignore the published accuracy gap, since it reflects how the two divisions test rather than how the movements run.
Related Guides
- Seiko 5 accuracy: what spec to actually expect: what these movements really do day to day, against what the paperwork claims.
- How to regulate a Seiko automatic at home: including why the 7S26 and the 4R36 need different lift angle settings.
- Why is my Seiko automatic watch losing time?: the seven causes worth checking before blaming the calibre.
Image credits: Seiko 5 Sports by Daniel Zimmermann. Seiko Monster and SKX divers via Wikimedia Commons.
