Here is a photo of Cousteau's very first regulator, a home-made job designed by both Cousteau and Emile Gagnan, who was working for Air Liquide at the time. The design came from a propane regulator Gagnan had designed for cars to run on propane or natural gas, rather than gasoline during the occupation by Nazi Germany of France during WWII.
We have a great community here, and enjoy discussing the old gear. Here is the Cousteau-Gagnan 45 regulator, which is the first regulator marketed in the USA (designed in France though) through U.S. Divers Company. It was known as the DA Aqua Lung regulator.
John C. Ratliff Diving since 1959, at age 13. Haven't stopped, and still enjoy getting wet.