Hopper Window Lock

I'm afraid that I don't know what this piece is. What does it do? Could we see a photo if it installed? Hopefully that information will help us track it down. Thank you!

Perhaps I can help. I believe you have what we referrer to as a basement hopper window. Your lock looks like it could be a type of spring-loaded hook. The type of hopper window locks we carry are like the 38-126. If you're seeking the exact lock you have, you will need to try and contact the manufacturer of the window to see if they still have it in supply.