Yes Sl68s are nelson based.
Here is the parts explosion I made for the 007, on page two you will notice the internals, any gun that uses inernals like these is nelson bassed.
http://www.mcarterbrown.com/gallery/.../Nelspot11.JPG Cover (page 1)
http://www.mcarterbrown.com/gallery/.../Nelspot21.JPG Page 2
http://www.mcarterbrown.com/gallery/.../Nelspot31.JPG Page 3
http://www.mcarterbrown.com/gallery/...0/Nelspot4.JPG Page 4