Sellita Cal. SW501 a is a clone of the ETA/Valjoux 7750 automatic chronograph with day and date. In production since 2009, Cal. SW500 is used by a wide variety of manufacturers and is sometimes even referred to as “7750”. One notable difference is the use of an eccentric screw regulator rather than the Valjoux index system. The “501 a” name has only been seen since 2017, though the availability of a 15 minute day-and-date SW500 movement from Sellita might pre-date this name.
This movement features the classic Valjoux 7750 subdial arrangement with running small seconds at 9:00, a 12 hour chronograph counter at 6:00 and a 15 minute chronograph counter at 12:00. Day and date windows are placed at 3:00.
Sellita SW500 and SW600 Technical Information
The Sellita SW500 and SW600 movements are based on the Valjoux 7750 design, itself based on the Valjoux 7733 and Venus 188. This movement is known for durability and flexibility and is used as a base in many watches, from entry-level chronographs to the famous IWC “Il Destriero Scafusia” grande complication. It is a large and relatively thick movement, measuring 13.25 ligne (30.00 mm) in diameter and 7.90 mm thick.
Although based on a classic design, the modern SW500 and SW600 is robust and full-featured. It operates at 4 Hz (28,800 A/h) with an efficient uni-directional central winding rotor. The day and date wheels feature crown-operated quick correction and a stop seconds (“hacking”) feature is included. The base movement has the famous Valjoux 6-9-12 subdial layout with small seconds at 9:00, but many Sellita versions have other subdial designs.
One major differentiator for the Sellita movements is the use of an eccentric screw for regulation rather than the traditional Valjoux articulated index.
