Need replacement Part

I'm afraid I can't determine what you have based on this photo. I assume at this stage that what you need is a balance, which is the spring-loaded mechanism on either side of the window that regulates its operation. However in order to identify that, I'll need you to remove an undamaged model from the window and show us a clear, unobstructed photo of the part in its entirety.

Please note that I may have more questions for you after I see that, but I need to know what to ask for, first.