Some light hints that may point you in the right direction:
Hint 1
The assembly is a part of a larger machine.
Hint 2
Several assemblies are meant to move side by side in unison.
Hint 3
The square-ish shaped piece is plastic that will wear down and be replaced.
God damn. That's the hardest one I've seen in a long time. Very nice.
I figured it would be a tough one.
These are mail insertion machines I worked on for several months as a mechanic. It's a little blurry since that were moving, but here it is in action:
That's cool. Never seen anything like that. I love big industrial machines that exist only to recreate an action a single human can do easily lol