Heuer, Breitling and Hamilton introduced their automatic “Chronomatic” chronographs at press conferences held on March 3, 1969, and these three companies also featured these new chronograph at the Basel Watch Fair held in early April 1969. Sales of the watches began soon thereafter, through retailers in major markets around the world.
In our posting, “Project 99: The Race to Develop the World’s First Automatic Chronograph”, we tell the story of how the joint venture between Heuer, Breitling, Hamliton-Buren and Dubois-Depraz developed the Chronomatic movement. As a part of that joint venture, on August 1, 1968, representatives of Buren filed an application with the United States Patent Office for “A Self-Winding Wristwatch with a Chronograph Mechanism”. The patent application was granted on December 1, 1970.
To see the patent documents, have a look at “United States Patent for Self-Winding Chronograph“.