Interesting gun you refer to. I don't think it qualifies as having a Jones system though since the cam only works on one notch. The great strength of a Jones came from caming down opposite facing cuts in the underlug. And then there is apparently a second lockup coming in from the rear of the action. Probably was an attempt to circumvent Purdey's patent for their double under bolt.
Here is a gun with a true Jones action. Probably the strongest lockup system ever devised, and it was patented in 1857! Notice the double cams.
