Movements

NH70 vs NH35

The NH70 keeps the NH35's running figures and hand sizes and changes almost everything you can see, plus the parts that hold it in the case.

By Stephen V. · Updated Sep 17, 2026

The NH70A is a skeletonized, no-date relative of the NH35A. Both run at 21,600 vph with 24 jewels, a reserve of more than 41 hours, hacking and hand-winding, and the same hand-hole sizes. The NH70 is nickel-plated and open-worked, uses a ring dial instead of a full dial, drops the date, and is held in the case by different parts.

Side by side, from the spec sheets

Both columns come from Time Module’s specification sheets for the NH35A and NH70A, and the NH7 series technical guide:

Time Module specification sheets — NH35A and NH70A
	NH35A	NH70A
Display	Three hands with date	Three hands (skeleton)
Finish	—	Nickel plating
Diameter	27.40 mm (29.36 mm with dial holding spacer)	27.4 mm outside, 27.0 mm casing
Height	5.32 mm	5.32 mm
Jewels	24	24
Frequency	21,600 vph	21,600 vph
Power reserve	More than 41 h	More than 41 h
Stated accuracy	−20 to +40 s/day at 23 ± 2 °C	−20 to +40 s/day at 23 ± 2 °C
Crown positions	Three (run, date, time)	Two (run, time)
Dial	Full dial, date window at 3, 6 or 9	Ring dial, 31.50 mm outer, 23.90 mm max inner
Hand holes (hr / min / sec)	1.506 / 0.891 / 0.215 mm	1.506 / 0.891 / 0.215 mm

What the skeleton changes: the look, and the dial

The NH70A’s sheet calls it “Three Hands (skeleton)” with “Nickel plating,” and TMI’s NH7 product page adds a Côtes de Genève decorated rotor. The same family comes in other platings: the NH71 in gilt and the NH72 in ruthenium gray. The point of the movement is to be seen, from the front as well as through a caseback.

That is why the dial changes shape. Instead of a full dial, the NH70 takes a ring dial — per the drawing, up to 31.50 mm across the outside with an opening of up to 23.90 mm — so the open-worked movement shows through the middle. Its dial feet are also in different positions from the NH35’s and a different size, which is our reading of the two drawings: an NH35 dial is not a drop-in part here, and it would hide the movement you bought the NH70 to show.

What it drops: the date

Like the NH38, the NH70 has no date and a crown with a single pull-out position, for the time. If a date is non-negotiable, the NH70 is the wrong movement.

What it keeps: the running figures and the hands

Underneath the finishing, the numbers are the NH35’s: 24 jewels, 21,600 vph, more than 41 hours of reserve, −20 to +40 seconds a day at 23 ± 2 °C, hacking, hand-winding and bidirectional automatic winding, and a 5.32 mm height. The hand holes are identical — 1.506 mm, 0.891 mm and 0.215 mm — and TMI’s catalogue lists the NH70, NH71 and NH72 in the same hand-height column as the NH35, NH36 and NH38. On the published dimensions, a hand set that suits one suits the others.

TMI does not describe the NH70 as a skeletonized NH38, and we will not either, but the two share the no-date layout, the single-position crown and the same hand fittings.

What changes in the case: the fitting

This is the part that catches builders out. The NH35A is 27.40 mm across and sits in a case at 29.36 mm with its dial-holding spacer. The NH70A’s casing diameter is 27.0 mm, and its drawings specify a dial support ring and casing clamps, with a stainless steel casing ring of 32.30 mm. A case machined for an NH35 is not automatically a case for an NH70; check that the case is sold for the NH7 series, with its ring, before buying the movement.

The casing notes differ too. The NH35A sheet says a screw-type case back is required and “Non-corresponding with Diver’s watch.” The NH70A sheet keeps the second line and does not list the first. Neither is specified for a certified diver.

Legibility is the trade-off nobody lists

A skeleton movement is busy by design, and busy is the enemy of reading the time at a glance. The hands on an NH70 build sit over plated bridges and wheels rather than over a plain dial, so hand color and finish do more work than they do on an NH35. If the watch is for looking at, that is the appeal. If it is for reading quickly, the NH35 is the better tool. Lume helps in the dark; it does nothing for contrast in daylight.

Which one to choose

Choose the NH35 for a date, a full dial, the widest choice of cases and dials, and the most legible watch.
Choose the NH70 (or the gilt NH71 or ruthenium NH72) when the movement itself is the dial and you have a case built for the NH7 series.
Choose the NH38 if you want to see the balance but keep a full dial — its open heart is a window, not a skeleton.

Nothing to buy on this page, deliberately

No finished watch in this site’s product registry runs an NH70, and we do not put a buy button on anything we have not verified there. For finished watches to build on, see the best Seikos to mod; for the base movement in full, the NH35 reference.

What we are not claiming

We have not handled, opened or timed either movement. Figures are transcribed from TMI’s sheets, drawings, technical guide and catalogue, with drawing units converted from hundredths of a millimeter. The dial-foot comparison is our reading of the two drawings, and the page says so where it relies on it.

Questions

What is the difference between the NH70 and NH35?

The NH70 is skeletonized and nickel-plated, uses a ring dial, has no date, and is held in the case by a casing ring and clamps. Its running figures — 24 jewels, 21,600 vph, more than 41 hours, −20 to +40 seconds a day at 23 ± 2 °C — and its hand-hole sizes match the NH35.

Does the NH70 have a date?

No. It is a three-hand movement with a single pull-out crown position for setting the time.

Will an NH70 fit an NH35 case?

Not automatically. The NH70A’s casing diameter is 27.0 mm and its drawings call for a dial support ring, casing clamps and a 32.30 mm casing ring, while the NH35A sits at 29.36 mm with its spacer. Use a case sold for the NH7 series.

What are the NH71 and NH72?

The same skeleton family in different finishes: TMI lists the NH71 in gilt and the NH72 in ruthenium gray plating, against the NH70’s silver nickel plating.

Do NH35 hands fit an NH70?

On the published dimensions, yes: both sheets give hand holes of 1.506 mm, 0.891 mm and 0.215 mm, and TMI lists them in the same hand-height column.

Sources

Specifications are transcribed from manufacturer documentation and published standards. Where a manufacturer does not publish a figure, this page says so rather than estimating one.