Greenwood mentions the name „Rissack, Liege, Belgium“ as a possible real maker of these needlefire rifles, merely finished and retailed by British gunmakers. Here you may see a pistol by J.J.Rissack, Liege, with this type of action. Scroll down to near bottom of page.
http://www.littlegun.be/arme%20belge/art...acques%20gb.htm