In 1960s Switzerland, three manufacturers competed for the chronograph market: Lemania, Valjoux and Venus.
Venus made the Calibre 175 column wheel chronograph movement used in watches during World War II and into the 1960’s. Breitling used the Venus 175 in her pilot watches and they remain desirable collectors items today. You can find listings of vintage on eBay in the vicinity of $2500 to $5000.
Lemania had a large share of the chronograph market and helped Hamilton release their chronograph. That meant NATO military contracts with the highly praised Hamilton chronograph.
Valjoux began to emerge as the technology leader after acquiring Venus in 1966.
Before Valjoux bought Venus, the company attempted to raise working capital. Of their many efforts, Venus sold their existing Caliber 175 machinery, materials and designs to China.
In the 1960s, the Chinese Ministry of Light Industry kicked-off several projects to develop Chinese-made clocks and watches. The Code 304 project developed, tested, and sourced a Chinese-built chronograph wrist watch for air force personnel – watches for MIG fighter pilots!
In 2011, Seagull reissued their 1963 Venus based chronograph as a limited edition. It proved so popular, the company decided to make a permanent offering of Chronographs similar in design to the ‘304.
You can see the watch below in search results on eBay
Hamilton went head-to-head with Seagull in 2011 marketing two retro Chronographs. Seagull reissued their ‘304 Airforce chronograph’ also now as the 1963 Seagull ST19 Pilots watch.
Hamilton Watch released a military chronograph in 2011, called the Khakhi Aviation Pilot, to compete with the Chinese Pilot. You can see it also in a search on eBay
Hamilton did make a market in Pilot chronographs that appealed to western tastes. The design below brought the price closer to the Seagull offering without critics devaluing the watch. Hamilton used several names for this design. They call the preowned one below a Jazzmaster Chrono. Hamilton also released this watch as a Jazzmaster with a Guilloche Dial and a Jazzmaster Pilot. It has a 251.474 ETA Quartz movement.
You can find more information about the early Hamilton chronographs on a forum thread at watchuseek
Jeffrey Stein wrote a thorough article called: Project 99 — The Race to Develop the World’s First Automatic Chronograph