Andreas - all 2-triggered doubles I know of, whether shotgun or rifle, muzzleloaders or ctg. guns, fire the right barrel with the front trigger. This gun appears no different.

I've always thought an "articulated" trigger meant the front trigger will push forward to prevent cutting your trigger finger when firing the left barrel. Indeed, in the last picture, the hinge pin in the front trigger appears. (If that indeed is what THIS system is) If not, I would like to know what it is.