Sea-Gull ST5 wristwatch with 19 jewels. This is an extremely important model in the history of Chinese watchmaking, which was produced in the Tianjin factory between the 1970s and 1980s.  Manually wound caliber ST5 (19 jewels), which was the first movement entirely designed, developed and manufactured in China. The movement is highly prized by collectors for its unique, hand-engraved wavy lines on the movement bridges (so-called "Sea-Gull stripes").