HANBORO 5378 Chime Automatic Watch — Modified Miyota 9015, Hourly Bell, Open-Heart, 41.5mm

HANBORO 5378 Chime Automatic Watch — Modified Miyota 9015, Hourly Bell, Open-Heart, 41.5mm

The HANBORO 5378 is a 41.5mm modified Miyota 9015 automatic watch with an integrated hourly chime complication — a mechanical hammer strikes a bell at each hour, audible as a single clear tone, with the hammer assembly visible through an open-heart aperture at 7 o’clock. Modified for 60-hour power reserve (above the standard 9015’s 42 hours), 24 jewels, 28,800 vph, red sweep seconds hand, textured granular dial surface, 904L stainless steel case, sapphire crystal and caseback, 100m water resistance, 22mm-to-18mm tapered bracelet. Four variants: two dial colours (navy blue, sky blue) × two strap types (stainless steel bracelet, black leather strap).

Key Specifications

Variants — Four Configurations

5378-1: Navy-blue textured dial, silver case, stainless steel bracelet — the most formal and broadly wearable combination.

5378-2: Sky-blue textured dial, silver case, stainless steel bracelet — the lighter and more contemporary blue on the same bracelet configuration.

5378-3: Navy-blue textured dial, silver case, black leather strap — dress-sport character; the leather shifts the watch toward more formal contexts.

5378-4: Sky-blue textured dial, silver case, black leather strap — the freshest and most casual of the four.

The Hourly Chime Complication

A mechanical chime in a wristwatch is one of the rarest and most mechanically demanding complications. In traditional watchmaking — Grand Sonnerie, Minute Repeater, Quarter Repeater — striking mechanisms add significant cost and complexity. The HANBORO 5378 integrates a simplified hourly striking mechanism driven by the modified Miyota 9015 base movement.

How it works: At the top of each hour, the chime mechanism releases a spring-loaded hammer that strikes a small metal gong or resonator within the case, producing an audible bell tone. The single strike marks each hour — one clear note.

Open-heart at 7 o’clock: The dial aperture at 7 o’clock exposes part of the hammer assembly. As the mechanism fires at each hour, the hammer movement is visible through this aperture — a brief, precise mechanical motion confirming the chime has operated.

Dedicated pusher: A separate crown or pusher controls the chime function — enabling or disabling the audible strike as required. In situations where the hourly chime is not appropriate, it can be deactivated without affecting timekeeping.

Modified Miyota 9015 — 60-Hour Reserve

The standard Miyota 9015 delivers approximately 42 hours of power reserve. The HANBORO modification extends this to 60 hours — typically achieved through an upgraded or extended mainspring. At 60 hours the watch runs for 2.5 days unworn without stopping, well above the 42-hour standard.

The Miyota 9015 is the highest-specification standard Miyota automatic — 28,800 vph, hacking seconds, hand-winding, 24 jewels. Used across San Martin SN0150, SN0148 and other quality watches in the range. The HANBORO modification adds the chime architecture to this reliable base while extending the power reserve.

904L Stainless Steel

904L is a marine-grade stainless steel alloy with higher chromium, molybdenum and nickel content than the 316L used in most watches in the range. It offers superior corrosion resistance in saline and acidic environments and takes a higher polish. 904L is most commonly associated with Rolex production — it is more expensive to machine than 316L and significantly rarer across affordable watch brands. For a watch designed with water exposure in mind (100m rating), 904L provides additional long-term corrosion confidence.

100m Water Resistance

100m / 10 ATM is swimming and recreational water use specification — suitable for:

• Daily wear
• Swimming
• Snorkelling
• General water activities

Not rated for scuba diving or saturation diving. At 100m the HANBORO 5378 is genuinely water-activity capable beyond splash resistance.

Textured Granular Dial

The dial surface uses a fine granular texture — small regular surface variations that create directional light scatter rather than the smooth reflective surface of a sunburst or matte dial. The texture adds visual depth to the blue colour field, shifting between lighter and darker areas as ambient light angle changes.

Who Is the HANBORO 5378 For?

The 5378 is built for:

• Hourly chime buyers who want a mechanical striking complication at an accessible price — the rarest complication in the range by a significant margin
• Modified 9015 buyers who want the extended 60-hour reserve on the Miyota 9015 base with additional complication
• 904L stainless steel buyers who want the marine-grade alloy on a sports-adjacent dress watch
• Sky blue dial buyers who want the fresh turquoise tone on a feature-rich automatic

How It Compares

vs. Farasute NL007B-1 Jump Hour — The Farasute is a visual complication (unusual time display). The HANBORO is an auditory complication (hourly chime). Both are unusual mechanisms in the affordable automatic category — different types of mechanical interest.

vs. Merkur Tourbillon — Both are unusual mechanical complications. The HANBORO uses a chime mechanism on a modified 9015; the Merkur uses a genuine tourbillon. Both represent complications rarely available at this price tier.

vs. San Martin SN0150 MOP — The San Martin uses an unmodified Miyota 9015 at 39mm/10.2mm as a dress diver. The HANBORO uses the modified 9015 at 41.5mm/12mm with chime mechanism. Same base movement, completely different complication focus.

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