These are MUST reads from Historical Diver Magazine directly relating to double hose regulator history and timeline. Pictures alone are priceless!!! All of these are available as back order issues through the Historical Diving Society.
HDS Volume 11 Issue 1 Number 34 A Guide to American Two Hose Aqua-Lung Regulators 1949-1973 by Mark Howell...
HDS Volume 11 Issue 4 Number 37. Cousteau's Magnificent "Alarm Clock" by our friend Nick Icorn.
French Cousteau Gagnan Regulators of the 1940's by Leslie Leaney.
The Rare SPACO Aqua Lung by Mark Howell.
HDS Volume 13 Issue 1 Numbere 42, Winter 2005. The entire issue is devoted to the early Aqua-Lungs...Authored by our friend Phil Nuytten