by I Pik U » 28 Oct 2006 19:05
Is it a flat spring? It looks to be a spring from one of the two buttons on either side of the latch, to keep the button/s in either position, pushed in or out.
Try moving the two buttons back and forth. If there's nothing holding/keeping the buttons detented in place, then I think that spring is meant to do that job.
Look at the shape of the spring, and puzzle in where it seems to fit to do the job.
Often opening up a Mortise Lock, parts will pop out of place. If it's the first time you've seen that particular model, it can be a puzzle figuring out how the parts go back togther.

Been playing with locks since '68.