Back to the original question

only H&H made "Paradox" guns/rifles

It held the patent for choke/rifling at the last 2" of bore

When the patent expired others i.e. WR Explora and others used the principles for rifled bore/shot guns

Bore rifles and s smooth bore guns existed before cartridge arms

The jug choke was used in the conversions of percussion to cartridge arms
I have a WW Greener converted 4 bore with such a "Jug" choke

TH44