Grail Watch Reference

A Reference Library for Watches from Grail Watch

Seiko 7S25

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The Seiko Cal. 7S25 is a mainstream automatic movement with date produced by Seiko Instruments Inc. (SII). It was introduced in 2004 for a new line of mechanical Seiko Prospex diver watches, SBDA001, which was produced through 2010. Cal. 7S25 is very similar to Cal. 7S35 and 7S55 but with 21 jewels instead of 23. It is also quite similar to Cal. 7S26, which adds a day wheel. Unusually for the 7S family, the 7S25 was only produced in Japan.

Cal. 7S25 was also sold by Time Module Inc. (TMI) as Cal. NH25 at least from 2008 through 2014. In this form, Seiko specified accuracy of -25/+35 seconds per day and a power reserve of “more than 41 hours”. Seiko also specified total height as 5.32 mm.

Cal. 7S25A was the original movement, produced from about 2005 through October 2006, when Cal. 7S26B was released. These feature updated parts on the balance staff, including an open-ended balance stud. It was further updated by 2011 to become Cal. 7S25C, the final version. This uses a different date disc and jumper, hour wheel, minute wheel, balance cock, ratchet wheel, first wheel, pawl lever, barrel and bridge, center wheel bridge and pinion, yoke spring, setting lever, and clutch wheel than versions A or B.

Soprod A10 Family

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The Soprod “Alternance 10” (also called the A-10, A10, and A10-2) is a Swiss Made movement based on the Seiko 4L25 design but produced in Switzerland under license. It is an advanced, slim automatic movement with modern technology and is not a clone of the ETA 2892A2 with which it competes.

The A10 is instantly recognizable thanks to its counter-clockwise balance cock and automatic winding rotor mounted with three screws and seven ball bearings.

The Soprod A10-2 is based on a Seiko design

Although a Japanese design, it includes many signature Swiss features, including Incabloc Double-Cone shock absorbers and an oscillating pinion automatic winding switcher. It is exactly the same size as the ETA 2892A2, with the same locations for dial feet, crown, hands, and date window. This makes it a drop-in replacement when that movement is unavailable.

Seiko Instruments first designed their 4L25 to create an ETA 2892A2 competitor for the Swiss OEM market. Soprod announced their Swiss Made version, Cal. A-10, in 2004 and began offering it to Swiss watch makers. The company was not explicit about the design source of the movement. In 2007, Soprod was acquired by Peace Mark of Hong Kong for the company’s quartz movement operations in China, and the Swiss mechanical operations were sold to Festina Group the following year. Seiko introduced their own 4L25-powered Brightz and Credor models and Soprod continued to produce the A-10 and later the A10-2.

Soprod redesigned the Alternance 10 (Cal. A10) movement in March 2012, launching the Cal. A10-2. The A10-2 was renamed Cal. M100 in 2016 and continues in production today.

Nomos Alpha Family

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The Nomos Alpha family of movements is an evolution of the original Nomos 1 family, itself based closely on the classic Peseux 7001. The Alpha family was the first movement constructed in-house by Nomos in Glashütte, though the assortment was sourced from ETA. Although based on the 7001 design, the plates and bridges are entirely different and reflect the classic Glashütte three-quarter plate concept. Nomos also manufactured the wheels in-house.

Nomos counts the 2006 automatic Nomos Epsilon as their official first in-house movement. It added a Nomos-designed bi-directional automatic winding system to the Alpha base which was entirely novel.

Starting in 2014, the Alpha family movements are being phased out in favor of the newer DUW 4000/5000 family, which includes the in-house Nomos Swing System assortment.

Nomos initially used Greek letters exclusively when naming these movements. Over time, they began specifying the name in Latin characters as well (i.e. “ξ (xi)”) before moving almost exclusively to Latin characters (i.e. “Nomos Alpha”) in the 2010s.

Hand WindingAutomatic
No DateNomos α (Alpha)
Nomos Alpha.2		Nomos ε (Epsilon)
DateNomos β (Beta)Nomos ζ (Zeta)
World TimeNomos ξ (Xi)
Power ReserveNomos γ (Gamma)
Date and Power ReserveNomos δ (Delta)

Soprod A10-2

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The Soprod “Alternance 10” (also called the A-10, A10, and A10-2) is a Swiss Made movement based on the Seiko 4L25 design but produced in Switzerland under license. It is an advanced, slim automatic movement with modern technology and is not a clone of the ETA 2892A2 with which it competes.

Although a Japanese design, it includes many signature Swiss features, including Incabloc Double-Cone shock absorbers and an oscillating pinion automatic winding switcher. It is exactly the same size as the ETA 2892A2, with the same locations for dial feet, crown, hands, and date window. This makes it a drop-in replacement when that movement is unavailable.

Seiko Instruments first designed their 4L25 to create an ETA 2892A2 competitor for the Swiss OEM market. Soprod announced their Swiss Made version, Cal. A-10, in 2004 and began offering it to Swiss watch makers. The company was not explicit about the design source of the movement. In 2007, Soprod was acquired by Peace Mark of Hong Kong for the company’s quartz movement operations in China, and the Swiss mechanical operations were sold to Festina Group the following year. Seiko introduced their own 4L25-powered Brightz and Credor models and Soprod continued to produce the A-10 and later the A10-2.

The A10-2 was renamed Soprod M100 in 2016.

SW220-1

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Calibre SW220-1 supports bi-directional winding.

Many manufacturers base their movements on the Sellita SW200-1. Similar movements that vary only in decoration include Oris 735 and 751 and TAG Heuer Calibre 5 Daydate Link. Movements based on the SW200-1 with modules or more modifications include Mühle SW 220-1, Oris 743, 745, 747, 748, and 752.

ETA 2897

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ETA’s 2897 is a modular movement with power reserve indicator and date. It is derived from the similar ETA 2892A2 and is part of the third-generation ETA 2890 family. Cal. 2897 appeared in 2004, alongside ETA 2896, and remains in production today.

ETA 2896

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ETA’s 2896 is a modular movement with “big date”. It is derived from the similar ETA 2892A2 and is part of the third-generation ETA 2890 family. Cal. 2896 appeared in 2004, alongside ETA 2897, and remains in production today.

Unlike many other “big date” movements, Cal. 2896 uses two concentric overlapping discs to display the date at 3:00.

The IWC 30130 is a refinished ETA 2896.

ETA 2826-2

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ETA Cal. 2826-2 is an automatic movement with date. It is a new entry in the long-running ETA 2800 family, introduced in 2004. The predecessor Cal. 2826 was produced in extremely limited numbers between 1971 and 1977.

The date wheel is the defining feature of Cal. 2826-2. It uses two overlapping discs, with the lower disc numbered 1-16 and the upper disc 17-31 with an aperture between 31 and 17. This allows a larger than usual date to be shown at 3:00 on the dial. The overlapping disc arrangement differs from the traditional dual-disc big date complication at 6 or 12 in many other watches.