Sea-Gull

Tied for 9th according to your criteria

Manufacture founded in 1955 in Tianjin, behind China's first fully domestic mechanical watch. Has developed its own ST19 chronograph caliber since the 1960s (derived from the Swiss Venus, whose tooling it had acquired), and describes itself as a genuinely integrated manufacture mastering design, component manufacturing and final movement assembly — which it also exports wholesale to micro-brands worldwide (including Timefactors, Magrette, Orange Watch Co.).