D304 is a perfect combination of the classic vintage and contemporary style.
A Brief Introduction to D304
In April 1961, commissioned by the Ministry of Light Industry, the Tianjin Watch Factory initiated a secret project, coded D304, to research and develop an aviation chronograph for the Chinese Air Force. Borrowing design ideas from Venus 175, the special task force managed to trial-produce 32 pieces by December 1963. 1964 was the year to make improvements. D304 passed all tests, including accuracy, high-low temperature, vibration, anti-magnetic, and anti-moisture, in October 1965. Jointly approved by 21 administrative units in December 1965, it entered batch production, designated as caliber ST3. By October 1966, 1,400 pieces had been produced. A total of 3,000 pieces were produced by the end of 1968. The original D304 was made exclusively for the air force, never commercialized for sale to the general public.
Sea-Gull began reworking on ST3 in 2002. The escapement system was modified to increase its reliability. Modifications were also made to the structure, size, and cosmetic appearance of certain parts, as well as the versatility of various small components, the material used for the lever and spring. The improved ST3 is the current ST19 serials.
