Thanks for that. Yes, a little more research reveals that 'SN Stretcher' was a trademark that Dolby applied to the early versions of Dolby A. I'm sure that lots of studios must have used it but that most record companies didn't emblazon "Dolby System" on their discs. Some marketing hype being used here that may actually have been counter-productive - I wonder how many people didn't buy such discs thinking they'd need a Dolby decoder?!
Yes I thought as much that it was part of the recording process and not encoded on the LP but Turnabout Records did use DBX on a catalogue of there LP`s that had DBX that had to be decoded with a black box for higher dynamic range than a normal LP it was supposedly be 80 to 90 db. high dynamic range and they where QS encoded as well.