http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=425689#Post425689

Does anyone else remember seeing a hammerless Jones underleaver?
This is the first that I remember...but I am getting old.

I have seen several Alex. Henry rifles and a few H&H rifles built in this configuration. The link you posted was the first shotgun I have seen built in this manner.

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.

There's at least one Dickson Round Action rifle with a Jones under lever - a .450 if I remember correctly.

I've personally handled an H&H 16ga hammerless Jones underlever gun. The gun had a story...started life as a 12ga.

Here is one, a 20/.577 Alex Henry rifle...

I once had a Boss 12ga hammer gun (damn I love saying that) that was an 1860 pin-fire conversion and had what appeared to be a Jones under-lever. However it only had a single cam rather than the two cams which make the Jones such a strong lock-up...Geo