The world of horology is a diverse one, filled with a multitude of watch movements that power the timepieces we all know and love. Two such movements that have captivated the interest of watch enthusiasts and manufacturers alike are the Miyota Caliber 8315 and the Seiko (SII) Caliber NH35A.
Both of these automatic, self-winding mechanical watch movements are designed and crafted with the meticulous attention to detail that is characteristic of their Japanese origins, but each brings its own unique features and strengths to the table and are widely used by microbrands such as Borealis Watch Company.
This post will delve into a detailed comparison of these two movements, providing a comprehensive overview of their specifications, features, and current market prices.
Miyota Caliber 8315
The Miyota Caliber 8315, a product of Miyota—a division of the renowned Citizen Watch Co. Ltd., stands out within the brand's "Standard Automatic" watch movements line for its exceptional running time. This 21-jewel automatic movement offers a power reserve of over 60 hours, setting a record for Miyota as their longest running mechanical movement.
The Miyota 8315, manufactured in Japan, measures 26mm in diameter and 5.67mm in height. Its operation is characterized by a beat rate of 21,600 bph (3 Hz), and it employs a counterclockwise winding direction for its rotor. Notably, this caliber features a Parashock anti-shock system, which is designed to enhance the durability of the watch by absorbing the impact caused by sudden shocks.
The Miyota 8315 offers a range of functions including central hours, central minutes, central sweeping seconds, and a date calendar at 3:00. Additionally, it is equipped with hacking seconds and quickset date functions. In terms of accuracy, Miyota claims that the Caliber 8315 maintains an average accuracy rating of -20 / +40 seconds per day under normal operating conditions.
Notably, the 8315 is based on the 8200 series framework, meaning it is compatible with most caliber 82XX dials, hands, and cases. As of the time of writing, replacement prices for the Miyota 8315 range from $50 to $65 USD.
Seiko (SII) Caliber NH35A
On the other hand, we have the Seiko (SII) Caliber NH35A, manufactured by Seiko Instruments Inc. (SII), which is part of the globally recognized Seiko Group. This caliber is an upgraded version of the Seiko Caliber NH25A and has since become one of the world’s most popular automatic movements.
The NH35A, like its counterpart, is an automatic, self-winding mechanical movement. However, it features a slightly larger diameter of 27.4mm and a shorter height of 5.32mm. It includes 24 jewels and operates at the same beat rate as the Miyota 8315, at 21,600 bph.
The NH35A showcases a power reserve of 41 hours and employs a bi-directional winding rotor, known as the Magic Lever. The movement also supports hand-winding and uses the Diashock system, an effective shock-resistance mechanism developed by Seiko. Function-wise, it offers central hours, central minutes, central sweeping seconds, and a date calendar at 3:00 (though the location can vary depending on the dial design). Like the Miyota 8315, it also supports hacking seconds.
The NH35A, as stated by the manufacturer, maintains an accuracy range within -20~+40 seconds per day under normal conditions. Furthermore, the NH35A is essentially an unbranded version of the Seiko Caliber 4R35, demonstrating its versatile application in various watch designs. Replacement prices for the NH35A are found to range from $40 to $55 USD, making it a slightly more affordable option compared to the Miyota 8315.
Here's a quick comparison of the key specifications of the two movements:
- Miyota Caliber 8315: Miyota (Citizen)
- Seiko (SII) Caliber NH35A: Seiko Instruments Inc. (SII)
- Miyota Caliber 8315: 26mm
- Seiko (SII) Caliber NH35A: 27.4mm
- Miyota Caliber 8315: 5.67mm
- Seiko (SII) Caliber NH35A: 5.32mm
- Miyota Caliber 8315: 21
- Seiko (SII) Caliber NH35A: 24
- Miyota Caliber 8315: 21,600 bph, 3 Hz
- Seiko (SII) Caliber NH35A: 21,600 bph
- Miyota Caliber 8315: 60 hours
- Seiko (SII) Caliber NH35A: 41 hours
- Miyota Caliber 8315: Counterclockwise
- Seiko (SII) Caliber NH35A: Bi-directional
- Miyota Caliber 8315: Parashock
- Seiko (SII) Caliber NH35A: Diashock
- Miyota Caliber 8315: Central hours, minutes, seconds; date calendar at 3:00
- Seiko (SII) Caliber NH35A: Central hours, minutes, seconds; date calendar at 3:00 (sometimes other locations)
- Miyota Caliber 8315: Yes
- Seiko (SII) Caliber NH35A: Yes
- Miyota Caliber 8315: -20 / +40 seconds per day
- Seiko (SII) Caliber NH35A: -20~+40 seconds per day
- Miyota Caliber 8315: $50 - $65 USD
- Seiko (SII) Caliber NH35A: $40 - $55 USD
Conclusion Miyota 8315 vs Seiko SII NH35