I've seen quite a few speculations about JAD in the Tinplate forums. Here is the TTOS Bulletin where the first JAD Loco (the Hiawatha) was introduced.
May 1974 was a good year for standard gauge. Actually 2006 and 2007 isn't too bad for standard gauge either.
Check out John Daniel's (it's Daniel by the way) introduction to JAD. This is a small part of the story of Daniel and the various toy train hobbyists in California. I've heard some good stories. They were a very, very creative bunch (think Dick Mayer, Ward Kimball, John Daniel and on and on).
Check out John's write up below.
PS Join TTOS and be part of a whole bunch of people that are also nuts for standard gauge stuff (and tend to take matters into their own hands!)