Casement Window lock

This appears to be a very old style lock. We sell a few that are similar but without seeing the back end, which is in the frame, then we won't be able to narrow it down for you.

I'm also not sure how you're going to be able to unstick this. My first option when it comes to this sort of thing is to slip a card between the sash and frame to see if I can manually push the lock out of the way. If that's not an option, though, then you may need to cut this lock off in order to get the window open again.