CITIZEN NH9136-88H MECHANICAL MEN WATCH
NH9136-88H
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The Citizen NH9136-88H is an open heart — a cutaway in the dial exposing the balance wheel, so you watch the mechanism beating from the front rather than only through the back. Most mechanical watches hide their movement entirely. This one puts it on display twice over.
The setting is deliberately restrained so the cutaway carries the watch: a grey dial with Roman numeral markers and gold-tone hands, minute markers around the outer rim, in a 40mm two-tone case with a gold-tone bezel at 10.7mm thick. Grey is the quieter of the two dials in this line, and the one that lets the gold accents do the talking.
Inside is Citizen's Calibre 8229 — 21 jewels, 21,600 vibrations per hour, roughly 40 hours of power reserve. Sapphire crystal protects the front and a glass exhibition caseback shows the full movement at the rear. Water resistant to 50 metres, 130 grams, on a two-tone bracelet with a fold-over push-button clasp.
At a Glance
- BrandCitizen
- CollectionMechanical Open Heart
- MovementCalibre 8229 Automatic
- Case Size40mm
- Thickness10.7mm
- Weight130g
- DialGrey, Open Heart
- MarkersRoman Numerals
- Case FinishTwo-Tone, Gold Bezel
- GlassSapphire (Top)
- CasebackExhibition (Glass)
- Power ReserveApprox. 40 Hours
Why You'll Love It
- The open heart is genuinely uncommon at this price. A cutaway showing the balance wheel is normally a feature of watches costing several times as much — here it is the centrepiece of the dial.
- You see the movement from both sides. Sapphire on the front over the open-heart aperture, and a glass caseback at the rear showing the full calibre and rotor. Most watches offer one or the other.
- Watching the balance wheel oscillate is the most direct answer to "why buy mechanical instead of quartz" — it is the part that actually keeps time, moving several times a second, out in the open.
- Grey is the restrained choice in this line. Against the gold-tone bezel and hands it reads dressier and more neutral than a coloured dial, and it works with a suit without any thought.
- Roman numerals keep the dial traditional, which is the right counterweight to a technical feature like an exposed balance — the two balance each other rather than competing.
- Sapphire crystal resists the everyday scratches that haze mineral glass within a few years, so the dial stays clear and the open heart stays worth looking at.
- At 40mm and 10.7mm this is a moderate, wearable size — many open-heart watches run larger to make room for the aperture, so this is one of the more cuff-friendly examples.
- No battery, ever. The movement is wound by the motion of your wrist, so there is nothing to replace and no service appointment to remember.
Perfect For
- Mechanical Watch Enthusiasts
- Open Heart Collectors
- Two-Tone Watch Fans
- Office & Formal
- Neutral Dial Wearers
- First Automatic Watch
- Milestone Gift
- Anniversary Gift
Key Features
- Open-heart dial — a cutaway aperture exposing the balance wheel of the movement, visible from the front of the watch.
- Citizen Calibre 8229 automatic movement — 21-jewel self-winding mechanical movement running at 21,600 vibrations per hour with approximately 40 hours of power reserve. No battery required.
- Grey dial with Roman numeral markers — gold-tone hands and hour markers, with minute markers around the outer rim.
- Sapphire crystal — rated 9 on the Mohs hardness scale, over the dial.
- Glass exhibition caseback — a see-through back displaying the full movement and oscillating rotor.
- 40mm two-tone case — 10.7mm thick, silver-tone with a fixed gold-tone bezel, weighing 130 grams on the bracelet.
- Two-tone bracelet — matching the case, with a fold-over clasp and push-button release.
- 50-metre water resistance (5 BAR) — rated for handwashing, rain and brief immersion. Not intended for showering or diving.
Technical Specifications
The Citizen NH9136-88H is a 40mm men's automatic watch from Citizen's Mechanical Open Heart line, powered by Calibre 8229 with 21 jewels, a 21,600 vph frequency and approximately 40 hours of power reserve. The two-tone stainless steel case measures 10.7mm thick with a fixed gold-tone bezel, sapphire crystal over the dial and a glass exhibition caseback. The grey dial carries Roman numeral markers, gold-tone hands, minute markers around the outer rim and an open-heart aperture exposing the balance wheel. It weighs 130 grams on a two-tone bracelet with fold-over push-button clasp and is water resistant to 50 metres.
| Model Number | NH9136-88H |
| Case Material | Two-Tone Stainless Steel |
| Case Diameter | 40mm |
| Case Thickness | 10.7mm |
| Weight | 130g |
| Bezel | Fixed, Gold-Tone |
| Crown | Push-Pull |
| Glass | Sapphire Crystal (Top) |
| Caseback | Exhibition — Mineral Glass |
| Water Resistance | 50 Metres (5 BAR) |
| Colour | Grey |
| Aperture | Open Heart (Balance Wheel Visible) |
| Markers | Roman Numerals, Gold-Tone |
| Hands | Gold-Tone |
| Minute Track | Outer Rim |
| Display | Hours, Minutes, Seconds |
| Material | Two-Tone Stainless Steel |
| Clasp | Fold-Over with Push-Button Release |
| Calibre | Citizen 8229 |
| Type | Automatic (Self-Winding) |
| Jewels | 21 |
| Frequency | 21,600 vph (6 beats/sec) |
| Power Reserve | Approx. 40 Hours |
Best Matched With
- Charcoal Suit
- White Oxford Shirt
- Navy Blazer
- Grey Merino Knit
- Brown Leather Belt
- Cream Trousers
- Camel Overcoat
Frequently Asked Questions
What is an open-heart dial?
A cutaway aperture in the dial that exposes part of the movement underneath — specifically the balance wheel, the component that oscillates back and forth to regulate timekeeping. It moves several times a second and is the part of a mechanical watch that is genuinely alive to look at. Most watches hide it entirely behind the dial.
Can I see the movement from the back as well?
Yes. The caseback is glass, so the full calibre and its oscillating rotor are visible from behind while the balance wheel shows through the dial at the front. Being able to see the movement from both sides is unusual at this price.
How does this differ from the green version?
Same 40mm case, same Calibre 8229, same sapphire crystal and glass caseback — the dial changes. The NH9136-88H has a grey dial, the more neutral and formal of the two. The NH9134-83X uses a green dial, which is warmer and more distinctive. Both carry Roman numerals and the open-heart aperture.
Is the case gold or steel?
Two-tone — stainless steel with a gold-tone bezel and gold-tone elements through the bracelet. It is not solid gold. Two-tone also means it sits comfortably with both silver and gold jewellery, which a single-finish watch cannot.
What does "automatic" mean?
An automatic watch is powered by the natural movement of your wrist. A rotor inside the case winds the mainspring as you wear it, so no battery is needed. If left unworn for about two days it will stop and need resetting — simply wear it again to restart it.
How long does the power reserve last?
Approximately 40 hours when fully wound, so the watch keeps running for close to two days after you take it off. Regular daily wear keeps it continuously wound.
How accurate is a mechanical watch?
Mechanical movements are not as precise as quartz by design — expect to reset the time every week or two. The appeal is the engineering, the absence of a battery, and in this case the ability to watch the balance wheel doing the work.
Does a mechanical watch need servicing?
Yes. Unlike a quartz watch, an automatic has moving parts and lubricants that wear over time. Citizen recommends periodic servicing to keep timekeeping and water resistance within spec. Any City Chain outlet can arrange this — bring your warranty card.
Can I swim with this watch?
No. With 50-metre (5 BAR) water resistance it is rated for handwashing, rain and brief accidental splashes, but it is not intended for swimming, showering or diving. Steam and hot water are particularly hard on seals at this rating.
Will 40mm fit my wrist?
40mm sits in the middle of the modern men's range and suits most wrist sizes from roughly 15cm to 19cm. At 10.7mm thick and 130 grams it is moderate for an automatic — many open-heart watches run larger to make room for the aperture, so this is one of the more wearable examples.
Is the bracelet adjustable?
Yes. The bracelet can be resized by adding or removing links. City Chain offers complimentary bracelet sizing at any outlet — bring your warranty book along for the service.
What warranty does this watch come with?
The NH9136-88H comes with a 3-year warranty when purchased from City Chain Singapore, an authorised Citizen retailer. Keep your warranty card and proof of purchase — both are required when submitting the watch for service at any City Chain outlet.
Why Buy from City Chain Singapore
- Authorised Retailer 100% genuine Citizen product
- 3-Year Warranty Covered on every purchase
- Free Shipping All orders within Singapore
- Bracelet Adjustment Size it in-store
Extra $15 OFF with min. $200 spend
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Extra $30 OFF with min. $400 spend
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Caliber No.: 8229
Movement: Automatic (Mechanical)
Jewels: 21 jewels
Frequency: 21,600 vibrations per hour
Case & Build:
Case Size: 40mm
Case Thickness: 10.7mm
Case Material: Stainless Steel
Glass (Top): Sapphire Glass
Glass (Bottom): Mineral Glass
Strap: Stainless Steel Bracelet
Water Resistance: 50 metres
Delivery within Singapore
Order by 11AM
(Mon - Fri for faster processing)
Checkout options may vary depending on order value and eligibility.
• Free Speedpost Domestic Delivery — 1–2 business days
• Free DHL Domestic Delivery — next business day
• Express Delivery — S$30, order by 2PM
• Click & Collect — ready in 2–3 business days. Please wait for the collection confirmation email before visiting the store.
Weekend & Public Holiday Orders
Orders placed after the applicable cut-off time, on weekends, or on public holidays will be processed on the next business day. Delivery will take place on the next available business day based on the selected delivery service.
During peak periods, festive seasons, major launches or sale events, additional processing and delivery time may be required.
For online purchase, you can have bracelet or leather strap adjustments done at any City Chain store. Please bring along your warranty book for the service.
