It is my understanding that the German Giant strain was just a larger hardy strain of genetics that came from Germany a while back. Pete Wise was the guy who bought the originals, and then they were also distributed to other breeders.
Now, they have been thoroughly dispersed through the market and other genetics. However, I know that many people will call their dragons German Giants if they are just large and hardy, but there are not many physical differences to make you sure of it.
I know that Dragons Den has dragons they market as German Giant, and I have had a couple of those dragons, and they are great, though, it is hard to say that any german giant lines are "pure".
But, many breeders keep track of their genetics, and can give you a very accurate idea of what your getting. Rob and Vickie Dachiu, AlphaDragons, and Josh at Phantom Dragons do a great job at this, and I am sure there are others that are others that do just as well.
Hope this info helped.
Phil
