CITIZEN MECHANICAL NH9138-15A BLACK LEATHER STRAP MEN WATCH

The Citizen NH9138-15A belongs to Citizen's Mechanical Open Heart line, where a cut-out in the dial leaves the balance wheel visible as it swings back and forth. A silver dial with Roman numeral markers and blue hands keeps the overall look formal, while that one aperture turns an otherwise classic dress watch into something you find yourself looking at. The 40mm stainless steel case sits on a leather strap, which keeps the whole watch light and traditional on the wrist.

Driving it is Caliber 8229, a mechanical automatic movement with 21 jewels running at 21,600 vibrations per hour. It winds itself from the motion of your wrist, and can also be wound by hand through the crown when it has been sitting unworn. A transparent caseback shows the rest of the calibre and the winding rotor from the rear — so you can watch the movement from both sides, which is unusual at this level.

The 40mm case measures 10.7mm thick — restrained for an automatic that has to make room for an open dial aperture — and is protected by sapphire glass, the hardest crystal material Citizen fits. Citizen specifies 100-metre water resistance for this model, which is considerably more than most dress watches offer and makes it far less precious in daily use.

At a Glance

• BrandCitizen
• CollectionMechanical Open Heart
• MovementCaliber 8229 Automatic
• Case Size40mm
• Thickness10.7mm
• DialSilver with Roman Numerals
• HandsBlue
• Dial FeatureOpen-Heart Aperture
• CasebackTransparent
• GlassSapphire Glass
• StrapLeather
• Water Resistance100m

Why You'll Love It

• The movement is part of the design: The open-heart aperture leaves the balance wheel on show, oscillating steadily on the dial side — the detail that makes a mechanical watch worth looking at rather than just reading.
• Visible from both sides: Sapphire glass over the aperture at the front, a transparent caseback showing the calibre and winding rotor at the rear. Most watches at this level give you one view or the other, not both.
• Winds itself, or by hand when you prefer: Caliber 8229 is self-winding from wrist movement, and the crown lets you wind it manually to get it going after it has been sitting unworn.
• Formal dial, genuinely interesting detail: Roman numerals and blue hands on a silver dial keep it appropriate with a shirt and jacket, while the aperture stops it from looking like every other dress watch.
• Dress looks without the fragility: Sapphire glass, a 10.7mm case that slips under a cuff, and 100-metre water resistance — far more than most dress watches — so it handles everyday life rather than only special occasions.

Key Features

• Caliber 8229 Mechanical Automatic — self-winding movement with 21 jewels, beating at 21,600 vibrations per hour.
• Open-Heart Aperture — a dial cut-out exposing the oscillating balance wheel.
• Transparent Caseback — the calibre and winding rotor visible from the rear.
• Hand Winding — the movement can be wound through the crown as well as by wrist motion.
• Silver Dial with Roman Numerals — classic dress-watch legibility.
• Blue Hands — a contrasting colour detail against the silver dial.
• 40mm Stainless Steel Case — classic proportions for a men's dress watch.
• 10.7mm Case Thickness — restrained for an automatic with a dial aperture.
• Sapphire Glass — Citizen's hardest crystal material.
• Leather Strap — traditional pairing, fitted in store to your wrist.
• 100m Water Resistance — well beyond typical dress-watch specification.

Technical Specifications

Frequently Asked Questions

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