Grail Watch Reference

A Reference Library for Watches from Grail Watch

Seiko 6S Family

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A key part of Seiko’s resurgence in modern times was the Cal. 6S family of automatic chronograph movements. Although rarely seen, they demonstrated the company’s expertise along with the Cal. 9S movement family introduced at the same time.

Seiko called back many original watchmakers from retirement to develop the “phoenix” Cal. 6S78 movement. On introduction in 1998, it helped re-establish the company’s bona fides and was a halo offering for the domestic Credor brand. It is thoroughly modern, with a vertical clutch and column wheel, yet classical in look. It has a 6-9-12 subdial arrangement like the popular Valjoux 7750 family. Many models feature a date or power reserve complication as well, and hand-winding versions were also produced.

  • 6S78 (1998-2004) – 34 jewels, automatic, date, Credor
  • 6S28 (2005-2013) – 34 jewels, automatic, date, Credor
  • 6S37 (2001-2016) – 40 jewels, automatic, date, power reserve, Prospex/Brightz/Credor
  • 6S77 (2003-2005) – 40 jewels, automatic, date, power reserve, Credor
  • 6S96 – 38 jewels, automatic, no date, power reserve
  • 6S74 – 35 jewels, hand winding, no date, power reserve
  • 6S99 (2002-2005) – 35 jewels, hand winding, no date, power reserve, skeletonized

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.