|Winding:||Automatic, Bi-Directional Automatic Winding|
|Diameter:||25.60 mm (11.5 ligne)|
|Hands:||Central Hour Hand, Central Minute Hand, Central Seconds Hand, Open Heart at 6:00|
Sprod Cal. M100 “Balancier Visible” is an automatic movement with an “open heart” balance wheel visible at 6:00 on the dial. It is used by Perrelet as Cal. P-391.
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.Images are taken from official publications and are used here for commentary and educational purposes. Copyright is held by the original owner as noted.