This is a fantastic example of a homemade regulator from the 1950's.  It was most likely made using the July 1953 Popular Mechanics article and a WWII oxygen aviation regulator.  The regulator's diaphragm have to be "waterproofed" before using it as an underwater regulator.  I have not dived this regulator, but the few old timers that I do know that have all said it was a very hard breather.  I acquired this regulator in the Ocala area and I do not know who made it or the history of it.  If you happen to know the maker and or the history please contact me.