Project 304 chronograph
In 1961 the Ministry for Light Industry received the order to develop a new 'aviator's watch' for the People's Liberation Army Air Force. This was designated "Project 304". The Venus Watch Company, Switzerland, were wanting to offload the calibre 175 chronograph tooling to raise capital for development of their calibre 188. The USSR were not interested, but the Chinese were. The 175 tooling was purchased for Project 304 and installed at the Tianjin Watch Factory. By October 1965, the third test batch were completed and submitted to the Ministry and Air Force for approval, which was passed in December. The production version was designated ST3. By May the following year, 1400 chronograph watches had been delivered to pilots of the PLAAF. A seconds-only chronograph version was prototyped, but it did not enter production. A small test batch was produced bearing the WuYi brand.