In hindsight, I should have taken pictures of the basic sequence of engagement and geometry involved in how these triggers work. For those interested, I will try to describe the function.
If you look just above the boss where the front trigger is pivoted, you will see a horizontal limb with a fine notch filed in the end and a radius lump just above the notch. The notch engages a mating cut in the trigger. The raduis lump engages the long arched piece just forward and above. This piece with the arch is actually "L" shaped and pivoted at the front pivot boss. Notice near the end of the vertical section there is a step cut into the right side. This step acts as an engagement position for the long bar which is pivoted off the large round boss atop a triangular base near the center of the assembly.
Basically up to this point, we have a very fine release which is followed by a coarser realease of what may be called a transfer bar.
The rear of this bar, just to the right of the center pivot boss assumes a pointed raduis shape near its end. Look closely at the 1:00 o'clock position just above the circular section of the pivot boss. You can just see the end of the bar here, the lower part of this comes around to complete the radius. (partly hidden behind the circular pivot boss).
This radius matches the male radius on the bottom of the rear striking trigger. When in the engaged position, the striking trigger is restrained by the transfer bar lever.
In all, an interesting example of combining mechanical advantage principles, geometry and physics. The designer was able to control the release of a huge mainspring (thus speed) with a release that is almost imperceptable.
