Seagull ST3621 Manual-Winding Movement (6 O’Clock Small Seconds)

The Seagull ST3621 is a manual-winding mechanical movement based on the ETA/Unitas 6498-style architecture. Featuring a small-seconds display at 6 o’clock, it is widely used in larger dress watches, pilot watches, pocket-watch-style builds, and custom hand-wound watch projects.

Specifications:

• Manufacturer: Tianjin Sea-Gull Watch Group

• Calibre: ST3621 / TY3621

• Movement Type: Manual-winding mechanical

• Time Display: Central hour and minute hands

• Seconds Display: Small seconds at 6 o’clock

• Frequency: 21,600 vibrations per hour (3 Hz)

• Jewels: 17

• Power Reserve: Approximately 46–48 hours

• Overall Diameter: Approximately 37.2 mm

• Main Plate Diameter: Approximately 36.6 mm

• Height: Approximately 4.5 mm

• Winding: Manual, crown-operated

• Calendar Function: None

• Accuracy: Performance varies according to regulation, installation, position, and operating condition
  

Sea-Gull, ETA, and Unitas are trademarks of their respective owners. ETA and Unitas are referenced solely to describe the movement architecture; no affiliation, sponsorship, or endorsement is implied.