Gizmo is called a double set-trigger. Works as follows:
The front trigger is the only one that fires the rifle. By itself, it tends to have a trigger pill in the 4-8# range (typically). The rear trigger sets the front, giving it a much lighter pull. Ofter, there is a litte vertical screw between the two triggers. This adjusts the weight of the front trigger from won't fire at all (undesireable) to fires when you breath on it (maybe even worse). In between, you find the weight you like. Some people like a few ounces. Once you've set the front, you unset it by pulling the rear trigger and, while holding it back, pulling the front and easing it forrard. It is very prudent to practice this on an unloaded rifle or to empty the chamber before doing it in action. These tend to be popular on Continental rifles. Personally, I find them acceptable on rifles you"ll fire fron a rest or prone, likely to encourage an accidental discharge when used off-hand. I have even seen them on dangerous game rifles, and I recommend MUCH practice before using one on a large charging mass of hair and muscle.
